1.Diameter:50-219mm . 2.Length:150-3500mm . 3.Material: Iron,stainless, Rubber, ... type:DTII,DX,TR,DTL,TD75 and so on. Idler dia:50,60,63.5,76,89,102,108,114,127,133 ... so on.Selecting a idler,Confirming some parameters:Idler dia,Idler shaft dia,Idler tube thk,Idler length,Idler material.1.Stable ...