The standard ER collet is the most widely used clamping system in the world. Made from Alloy spring steel and fully hardened these ER collets are ideal for many machining applications including boring, milling, reaming, tapping and grinding. Unless specified differently all of our ER collets feature runout of .0003 Inches or less. MariTool has one of the most comprehensive ER collet selections available in the industry including ER collets in 64th sizes and oversize collets such as ER16 in 7/16, ER20 in 9/16, and ER32 in 7/8. ER collet sizes start at ER8 through ER50. Please click on item to see detailed dimensions for each collet.