For the relevant matching transfers, choose theĀ M size.
Cutter Square Base Measurements:
S - 25 mm (0.98 in)
M - 35 mm (1.38 in)
L - 45 mm (1.77 in)
XL - 55 mm (2.17 in)
All measurements are taken of the bases' exterior dimensions, rounded off to the nearest decimal.