A set of 8 adjustable reamers with a size range of 15/32"-1-1/32" (11.90-26.20mm). Each reamer has an adjustment range of 1/16" (1.58mm) except the two largest sizes which are of 3/32" (2.37mm) range. If you need to produce a perfectly sized and concentric hole in a bush or pivot ect then a reamer is the tool to use. Having a square drive end of 5.5-12mm makes them easy to use with a suitably sized hand tap wrench. Every engineer should have a set.