# Choi Implanter Sizes Explained: When to Use Each

- Canonical: https://www.hairtransplantsource.com/articles/choi-implanter-sizes-explained
- Site: Hair Transplant Source (https://www.hairtransplantsource.com)
- Topic: Instruments & Suppliers
- Author: Editorial Team
- Medically reviewed by: Dr. Burhan Terzioğlu (Hair Restoration Surgeon · Contributing Author)
- Published: 2026-04-26 · Updated: 2026-08-14
- License: educational content, not medical advice; do not republish without permission.

**Quick answer:** DHI cases use 3–4 Choi implanter sizes rotated within a single surgical day. 0.64 mm for single-hair grafts at the hairline edge, 0.80 mm for double-hair grafts in the frontal zone, 0.90 mm for triple-hair grafts mid-scalp, 1.00 mm for multi-hair grafts in the crown. Surgeons who use only one size produce uneven density that's visible at month 12.

The Choi implanter is the instrument that defines DHI as a technique. It combines recipient channel creation and graft placement into a single motion, eliminating the separate channel-creation step that FUE requires. The pen itself is mechanically simple — a hollow needle with a plunger mechanism — but the size selection across a single surgical day is where DHI technique meets DHI craft. This article walks through the four standard sizes, when to use each, and the rotation discipline that distinguishes clinic-grade DHI from marketing-grade DHI.

This is the deep dive on Choi implanter sizing — connecting to the surgical walkthrough in [DHI hair transplant step by step](/articles/dhi-hair-transplant-step-by-step) and to the broader [hair transplant instruments pillar](/articles/hair-transplant-instruments-guide).

## The four standard sizes

Most DHI work uses four implanter sizes:

| Size | Graft type | Recipient zone | Approx. share in case |
|---|---|---|---|
| 0.64 mm | Single-hair | Hairline leading edge, temple | 10–20% |
| 0.80 mm | Double-hair | Frontal zone, density work | 35–45% |
| 0.90 mm | Triple-hair | Mid-scalp, vertex transition | 25–35% |
| 1.00 mm | Multi-hair (4+) | Crown, dense-pack zones | 5–15% |

Distribution shifts by case type. A pure hairline reconstruction case is heavily weighted toward 0.64 mm and 0.80 mm. A crown-only case shifts toward 0.90 mm and 1.00 mm. A full-scalp case rotates all four sizes throughout the day.

The single-size strategy that some clinics market — "we do all our DHI with one implanter size for consistency" — is a marketing simplification, not a clinical practice. Single-size DHI produces uneven density and either looseness at the hairline or compression damage at the crown, depending on which size was chosen.

## Why size selection matters

The implanter size determines the recipient channel geometry. Three clinical effects:

**Effect 1: Placement security.** A graft sitting in a channel slightly larger than itself can shift, rotate, or pop out during the early healing phase. The hairline is the zone where even small displacement is visible at month 12 — a single graft sitting 1 mm forward of its planned position breaks the irregular-line pattern that makes the hairline read as natural.

**Effect 2: Graft viability.** A graft compressed into a channel slightly smaller than itself suffers mechanical damage at the bulb. The damage is invisible at placement but appears at month 6 as poor regrowth in those specific zones. The clinic auditing 12-month outcomes notices this as zone-specific density failures rather than generalised poor results.

**Effect 3: Healing pattern.** Each implanter size creates a recipient channel of corresponding diameter. Mismatched diameters produce inconsistent healing — some channels close cleanly, others remain mildly inflamed. The aesthetic effect at month 6–12 is a slightly textured recipient surface visible under specific lighting.

Trained DHI surgeons rotate sizes deliberately for each of these reasons. The rotation is not optional; it is the technique.

## The mid-case rotation discipline

A working DHI case might rotate sizes as follows:

| Phase | Time | Implanter | Activity |
|---|---|---|---|
| Hairline leading edge | Hour 1 | 0.64 mm | Single-hair grafts, irregular line shape |
| Frontal core | Hours 2–3 | 0.80 mm | Double-hair grafts, density build |
| Mid-scalp | Hours 3–5 | 0.90 mm | Triple-hair grafts, density work |
| Vertex transition | Hour 5 | 0.90 mm | Tapering density |
| Crown | Hour 6 | 1.00 mm | Multi-hair grafts, less critical density |
| Touch-up | Hour 7 | Mixed | Filling gaps, adjusting density inconsistencies |

The discipline is having the right pen in hand at the right time, with the loading technicians feeding pre-loaded grafts of matching size. A clinic that runs 4 sizes through proper rotation needs 2 loading technicians per surgeon to maintain pace; clinics with fewer technicians end up either pausing the surgeon between phases or letting the rotation slip.

## What happens when rotation breaks

Three patterns show up in clinics that don't rotate properly.

**Pattern 1: Single-size cases.** Surgeon uses 0.85 mm (or whatever default) for everything. Hairline leading edge has visible single grafts in oversized channels. Crown has tight 4-hair grafts compressed into too-small channels. Year-12 photos show characteristic uneven density.

**Pattern 2: Inconsistent rotation across operators.** First operator on the case rotates correctly; second operator (relieving for fatigue) uses different sizes for the same graft types. The recipient zone shows mid-scalp density inconsistency that the team didn't notice in real-time.

**Pattern 3: Wrong-size emergency substitution.** Loading technician runs out of pre-loaded 0.80 mm pens; team substitutes 0.64 mm or 0.90 mm because the surgeon won't pause. The 50–100 grafts placed during this substitution show as a cluster of inconsistent results at month 12.

The training programmes that drill rotation discipline are covered in [DHI hair transplant training explained](/articles/dhi-hair-transplant-training-explained). Most failures in this area are training failures more than equipment failures.

## Loading technique for each size

The smaller the implanter needle, the harder the loading. Each size has loading characteristics:

**0.64 mm:** Loading single-hair grafts requires the most precise technique. The graft must be oriented bulb-first, threaded into the needle without bulb compression. Loading technicians develop this skill across 50–100 supervised cases before becoming independent on this size.

**0.80 mm:** The most forgiving size for loading. Standard double-hair grafts thread cleanly. New loading technicians typically start their training on this size before progressing to others.

**0.90 mm:** Slightly more demanding because triple-hair grafts vary in shape. Some grafts have splayed roots that catch the needle wall; technique adjusts per graft.

**1.00 mm:** Easy to load mechanically (large diameter) but requires careful selection of grafts that genuinely have 4+ hairs — placing a smaller graft in a 1.00 mm channel produces the looseness problem described earlier.

The full team-side discipline for DHI loading is part of the broader [training a hair transplant team](/articles/training-hair-transplant-team) curriculum.

## Procurement and inventory

A working DHI clinic stocks pens in the following pattern:

| Size | Pens in active rotation | Sterilised standby | Total stock |
|---|---|---|---|
| 0.64 mm | 4–6 | 4 | 8–10 |
| 0.80 mm | 8–12 | 6 | 14–18 |
| 0.90 mm | 6–8 | 4 | 10–12 |
| 1.00 mm | 4–6 | 2 | 6–8 |
| **Total** | **22–32** | **16** | **38–48** |

Total kit cost at major suppliers: €1,500–€3,000 for a starter set; €3,000–€6,000 for a full operational stock with redundancy. Per-pen replacement cost: €60–€180 depending on brand. The maintenance and replacement schedule sits in [instrument maintenance and replacement cycles](/articles/instrument-maintenance-and-replacement).

## What the size choice does NOT change

Some marketing claims overstate what implanter size affects. Three things size does not significantly change:

- **Procedure duration.** A well-rotated DHI case takes the same overall time as a single-size case; the rotation is parallelised with loading workflow, not serialised.
- **Patient discomfort.** All sizes are within the comfortable range under proper anaesthesia. Patient experience does not differ measurably between sizes.
- **Healing speed.** Recipient zones with matched implanter sizes heal within the same window as single-size cases (1–2 weeks for crusting resolution).

What size choice does change is the long-term aesthetic outcome — visible at month 6–12 — and graft viability in zones where the size was wrong. The variables that matter for graft survival broadly are documented in [graft survival rate in FUE and DHI](/articles/graft-survival-rate-fue-dhi).

## Final framing

Choi implanter size selection is a per-zone discipline that depends on graft type, recipient zone, and case profile. The trained DHI surgeon rotates four sizes throughout a typical case; the clinic-grade DHI team has the loading workflow to support that rotation in real-time. Single-size DHI is not a faster or simpler version of the technique — it is an undertrained version that produces the inconsistencies the surgeon would have prevented with proper rotation.

For the broader DHI technique walkthrough, see [DHI hair transplant step by step](/articles/dhi-hair-transplant-step-by-step). For how DHI compares to FUE more broadly, see [FUE vs. DHI hair transplant comparison](/articles/fue-vs-dhi-hair-transplant-comparison).

## Sources and further reading

- Choi YC, Kim JC. [Single hair transplantation using the Choi hair transplanter](https://pubmed.ncbi.nlm.nih.gov/1430550/). *The Journal of Dermatologic Surgery and Oncology*. 1992;18(11):945–948.
- Parsley WM, Perez-Meza D. [Review of factors affecting the growth and survival of follicular grafts](https://pmc.ncbi.nlm.nih.gov/articles/PMC2956960/). *Journal of Cutaneous and Aesthetic Surgery*. 2010;3(2):69–75.

## FAQ

**Q: Why do DHI cases need multiple Choi pen sizes?**

Because graft sizes vary across the recipient zone. A single-hair graft placed in a 1.0 mm channel sits loosely and risks displacement; a triple-hair graft forced into a 0.64 mm channel suffers compression damage. Matching pen size to graft size protects both placement security and graft viability.

**Q: What's the most-used Choi size in a typical case?**

0.80 mm and 0.90 mm together cover roughly 60–70% of placements in a mixed-density case. 0.64 mm covers hairline single-hair work (10–20%); 1.00 mm covers crown and dense-pack zones (10–15%). Distribution shifts based on the specific recipient pattern.

**Q: Can a surgeon use just one size for the whole case?**

Marketing-simplified clinics sometimes claim this; clinical practice does not. Using one size produces predictable problems: looseness at the hairline (graft displacement), compression damage at the crown (reduced viability), or wasted channel diameter that allows uneven density. Trained DHI surgeons rotate sizes within each case.

**Q: How are Choi pens loaded?**

Each graft is loaded into the hollow needle of the implanter pen by a trained technician. Two technicians loading in parallel keeps pace with one operator placing. The loading technique requires care — crushing the graft against the needle wall during loading is the second-largest preventable graft loss in DHI cases after time-out-of-body issues.

**Q: How many pens of each size does a clinic need?**

Working stock for a clinic doing 1–2 DHI cases per day: 8–12 pens per primary size (0.80, 0.90 mm), 4–6 pens per secondary size (0.64, 1.00 mm). Total kit: 30–50 pens across all sizes, allowing for sterilisation cycles and replacement during cases.

**Q: How often are Choi pens replaced?**

Pens are reusable across many cases when properly sterilised and inspected. Replacement is typically driven by needle tip damage (visible bend or burr) rather than calendar cycles. A working pen lasts 50–150 cases under normal use; aggressive use or improper handling shortens this substantially.

**Q: Are there alternatives to the Choi system?**

Yes. Several manufacturers produce DHI-style implanters: Choi (the original), Lion, KEEP, and others. The mechanics are similar — single-motion implantation with sized needles — but specific feel and handling vary. Most clinics standardise on one system for team consistency.

**Q: What's the price range for a Choi pen kit?**

A complete starter kit (4 sizes, 8–12 pens per size, sterilisation tray, loading station): €1,500–€3,000 from major suppliers. Per-pen replacement: €60–€180 depending on quality and brand. Annual replacement cost for a clinic doing 100 DHI cases per year typically runs €600–€1,800.