... efficiency NOVO's timing pulley:1. Plain bore: MXL, XL, L, H; T2.5, T5, T10; AT5, AT10; HTD 3M, 5M ... , 8M, 14M.2. Taper bore: XL, L, H, XH; HTD 5M, 8M,14M.3. Material: Aluminium, Cast ... of good qualityCertification:We've been ISO9001:2000 certified since 2003. L-H Taper pulleys