This guide is for use with 2" (50 mm) and 2-1/2" (63 mm) CDI-5400 and 6400 flow meters. It includes a 3/16" drill bit, a 5/16" hex wrench, and an aluminum drill guide and is a cheaper option than the universal guide if you're only working with these specific pipe sizes. These guides can be attached to the pipe with a band clamp, a C-clamp, or a chain clamp.