A nice set of 7 small adjustable blade reamers ranging from 1/4"-15/32" (6.3-11.90mm). Each reamer has a range of 1/32" (0.79mm). These are used to size a hole exactly to the size you require. Simply adjust slightly each time until the required size is reached. As well as the hole being the correct size it will also be perfectly round, ideal for inserting locating pins etc. The reamers have a square head to enable a hand tap wrench to be used, one ranging from 3.5-10mm will be perfect.