Hold tap and reamer true, preventing breakage. Hardened and replaceable jaws.Holds tool true-perfect alignment to reduce tap breakage eliminated by a large extent Works on flat and curved surfaces. The tap wrench, which will handle from 2.5mm to 12 mm square, locates in a sleeve with a 40mm diameter base machined square to the bore to ensure perfect alignment. There is a triangular groove cut across the base for accurate tapping into circular bars or tubes. Two apertures in the side of the sleeve allow you to check the progress of the tap. Set consists of tapping guide, tap holder and jaw A for capacity 1/16" to 1/4” & Jaw B for capacity 1/4” – 1/2” / M6 – M12 Tap.