The bundle option in this listing is already listed at a discount :)
Each shape comes as a set of 2 cutters. Cut outs in the photo are of the size 20mm, note that the smaller options will naturally have a small middle portion.
Cutter Square Base Measurements:
Studs -
15 mm (0.59 in)
17mm (0.67 in)
20mm (0.79 in)
All measurements are taken of the bases' exterior dimensions, rounded off to the nearest decimal.