The light gun obsessors love this stuff. I know that with Parker, the numbers are the weight before finishing. I have a 20 and a 16. Made within two years of each other. 20 is 0 frame, 16 is 1 frame. both have 28" barrels. Weight on 20 gauge set: 3-0. Weight on 16 gauge set: 3-1. So they mean nothing until the gun is finished. The 16 weighs 1/2 lb more than the 20. Slighly larger frame but I attribute much of the difference to 1/2" more (and probably more dense) wood and a skeleton buttplate.