How to Use Dual Nail Forms: Sizing, Steps and 4 Ways to Use Mr Nail Sandwich Forms
By Edmond Lin, M1 Nail & Beauty Supply, Markham, Ontario. Last updated 29 October 2026. Size charts and directions come from Mr Nail's English website and Mr Nail's official store page in China.
A dual form is a clear plastic mold that you fill with gel and press onto the nail: the mold shapes the top of the extension, so you file far less than with a paper form. Mr Nail (美甲先生) makes two kinds. The single-piece Extension Nail Mold is the classic dual form. The sandwich dual forms add a second, bottom mold that tucks under the free edge and shapes the underside too, so the extension comes off the forms with its final shape.
In this guide
Single dual forms vs sandwich forms
| Single dual form | Sandwich dual form | |
|---|---|---|
| Parts | One top form | Top mold + bottom mold |
| Shapes | The top surface; the underside is whatever the gel does under the free edge | The top surface and the underside of the free edge |
| After curing | File and clean up the underside | Little filing: the underside comes out clean and smooth |
| Mr Nail range | Extension Nail Mold: W036, W048 to W053 and W549 3D French | W555, W556, W557, W558, W559 and W561 |
| Box | W036 and W549: 150 pcs; W048 to W053: 120 pcs | 240 pcs (120 top + 120 bottom molds), 8 pcs per grid |
What you need
- Prepped nails and your usual gel base coat
- A builder or extension gel, for example Extension Gel 40g, K207 Quick Cured Extension Gel or K208 Jar Extension Gel. Mr Nail says the sandwich forms work with milky, jelly and clear extension gels, and with acrylic
- A UV/LED lamp, a file and a gel top coat
- Dual forms in the right sizes for all ten fingers
How to choose the size
- The forms are numbered 0 to 14 (most single-piece shapes 0 to 11); 0 is the widest. Top and bottom molds with the same number belong together.
- For the top mold, go one size larger when in doubt. It must reach both stress points (the A and B points, where the free edge leaves the finger on each side).
- Size the bottom mold the other way round: if the matching number does not fit, go one size smaller. A bottom mold that is too big presses the extension too thin at the stress points, and it can break there.
- Try the forms on all ten fingers before you start and lay them out in order.
Step by step with sandwich forms
- Prep the nail, apply base coat and cure.
- Fill the top mold with builder or extension gel. Use a little less than you think: the wings on the bottom mold stop the gel from overflowing when you press.
- Press the top mold on from the cuticle, with the bottom mold tucked under the free edge. Look through the clear forms to check the gel reaches the edges with no bubbles.
- Or do it in two steps: set the top mold first and cure briefly to fix the back, then press the bottom mold underneath to shape the underside.
- Cure fully, pop off both molds, file the edges and finish with a top coat.
The guide lines on the forms help you line them up. They show on the extension after you remove the forms; file to shape and they disappear once gel goes on.
4 ways to use the molds
- Top and bottom together, as above. The top mold also works on its own, like a single dual form.
- Bottom mold instead of a paper form. Tuck it under the free edge and build the extension on top; the numbered sizes fit different fingers.
- Repairs. Tuck the bottom mold under a broken nail and fill the gap with gel.
- French. The back edge of the bottom mold has a French curve, so you can fill the bottom mold with gel and press it on as a shallow form.
Which shape to choose
| Shape | Looks like | Top mold length, size 0 to 14 |
|---|---|---|
| W558 short oval | Short with a rounded tip, a natural length for everyday wear. Mr Nail recommends it especially for smaller nail beds. | 24.36 to 19.35 mm |
| W559 short square | Short with straight sides and a square tip: clean and professional. Mr Nail recommends it for larger nail beds. | 27.92 to 20.86 mm |
| W561 arch scoop | A straight tip with soft corners that curves down at the free edge when seen from the side. | 34 to 19.68 mm |
| W557 oval | A long oval with a rounded tip; from the side the free edge curves gently down. | 37.92 to 30.76 mm |
| W556 long straight tubular | Long and straight, with parallel sides and a square tip. Mr Nail made it for clients who want a longer, slimmer nail without extra time spent refining the shape. | 50.5 to 41.8 mm |
| W555 thin trapezoid | A long, slim tapered coffin: the sides narrow toward a flat tip, and from the side the extension runs long and straight. | 50.95 to 42.23 mm |
The single-piece Extension Nail Mold comes in W036 long straight coffin with positioning lines, W048 flat straight trapezoid, W049 short coffin, W050 almond, W051 long coffin, W052 European trapezoid, W053 long square and W549 3D French, which has French smile guide lines along the form.
Troubleshooting
- The extension is too thin. Use a bottom mold one size smaller, or leave a little space between the molds instead of pressing them fully together.
- No bottom mold fits the finger. Every nail is different. Trim a bottom mold to the shape you need.
- The bottom mold bends inward a little. Its back edge is made thin so it tucks under the free edge, and the wings can pull it inward. It does not change the result.
- Gel squeezes out at the sides. Use less gel in the top mold. Clean up any overflow before curing.
Cleaning and reuse
The forms are PP plastic. Wipe them clean after each use and put them back in the box: the sandwich box keeps top molds in one row and bottom molds in the other, one size per compartment. Store single-piece forms flat so they keep their curve.
Frequently asked questions
Are dual forms reusable?
Yes. Wipe them clean after use and put them back in the box.
Can I use dual forms with acrylic?
Mr Nail lists the sandwich forms for hard gel, extension gel and acrylic systems.
Do I still need to file after using sandwich forms?
Only the edges. The bottom mold shapes the underside of the free edge, so it comes out clean and smooth.
What do the numbers on the forms mean?
They are the sizes, 0 to 14 for the sandwich forms, with 0 the widest. A top mold and a bottom mold with the same number are a pair.
How many forms are in a box?
Sandwich forms: 240 pieces, 120 top and 120 bottom molds. Single-piece forms: 150 per box for W036 and W549, 120 for W048 to W053.
Where can I buy Mr Nail dual forms in Canada?
M1 Nail & Beauty Supply stocks Mr Nail forms and extension gels in Markham, Ontario at wholesale prices, with in-store pickup and shipping across Canada.
See every Mr Nail product we stock in Markham, Ontario.
Shop Mr NailSize charts and directions come from Mr Nail's English website and Mr Nail's official store page. Sizes are measured by hand, so allow for small differences.
