The Robert Sorby modular stems and tool rests allows a woodturner to collect a number of tool rests at different sizes at a reasonable cost. There are 5 options for tool rests, three straight (100mm, 152mm, 228mm), an internal curve (228mm) and an external curve (228mm). All of these are made of hardened steel to limit the chance of nicks and dents that can affect their use. The same stems are compatible with the Precision Boring System.