Allen 12mm Alloy threaded deck bush 17-22mm A8539-17-BLACKAllen anodised aluminium 12mm threaded deck bush 17 22mm The aluminium range comes in both threaded and non threaded versions. The threaded through deck bush allows for a perfect fit to your deck and stops rope wear both top and bottom. Aluminium through deck bushes are available in a choice of 6 colours, allowing you to add a personalised touch.