11PCS ER20 Spring Collet Set TIR 0.0002inch / 0.005mm - Durable and practical. - Special angled slots increase rigidity. - Protects tool holder from contaminants. - Better overall balance of tool holder assembly. - Use with any standard ER collet chucks for coolant-thru tool applications. Specification Model: ER16 Material: Spring Steel Gripping Range: 1/8.3/32,5/32,3/16,5/16,1/4,11/32,7/32,3/8,7/16,1/2.