The SAS Extension tubes are designed to fit the HD range on wheel clamp and on steel wheels where the rims are dished. Often on wide tyres the rims are centrally placed in middle of the tyre, meaning the standard SAS clamp wheel bolt cover tube will not sit against the rim over the nut but float in front of it. The question is often asked, “why won’t my SAS wheel clamp fit my wheel?” here. To make it fit the extension tube covers the distance in the inside of the wheel to reach over the wheelbolt and clamp tight on the wheel.
The black plastic end cap shown in the photo on the end of the Extension tube is not supplied. You must take the one on the clamp already and put it on the extension tube, or alternatively, they can be bought as an additional accessory from SAS.