Harlingen ER-32 8mm Spring Collet ~ Runout is ≤0.~ All slits are spaced and ground evenly. ~ The powerful clamping ability and durability are ideal for boring, milling, reaming, drilling and tapping as well as grinding operations in high precision machining. Harlingen ER-32 8mm Spring Collet ~ HARLiNGEN® ultra precision ER collets are made of high performance, special Grade GCrlS bearing steel that has been fully hardened and precisely ground by experienced craftsmen.