This model is made of a little ring with 10mm of external diameter and 5 mm of internal diameter. The base has 5 difference tolerance fits: from 0 (10 mm), .1 (10.1 mm), .2, .5 and 1 (11 mm).

This model can also be functional to test your first layer: if the ring goes through the base with no changes in the resistance the base puts on the ring, then you have a perfect first layer; if you have problems, consider downloading a more accurate first layer test.