Ref: 307 3M Roloc Holders
3M™ Roloc™ No1, No2, No3 and No4 holder for twist fit type discs, this holder / back up pad has a deeper internal thread to accept various discs. it come with 6mm shaft and it available as:No.1 - 25mm, No.2 - 38mm, No.3 - 50mm & No.4 - 75mm.
Will also accept the following disc types:
Norton - Speedlock Type R, Standard TR (Lockit), Pferd Type CDR, Sait SAIT-LOK-R, Klingspor QRC, Garryson Type R, Sia Siafix, amongst others.