Series 50 All Purpose Cheek Block - SingleFeatures:Exceptionally high working loadsLow maintenance, long service lifeSelf-lubricating Acetal polymer sheave ensures low friction and extreme durabilityAll purpose (AP) blocks are a great all around solution. Self-lubricating Acetal polymer sheaves running on polished stainless steel races perform equally well with dynamic loads and high static loads. For durability and a long service life, these blocks are the right choice for sheets, halyards and control line applications for cruising and racing.Can be mounted on masts and booms using the curved surface adapter. Can be stacked to create a double version, but no more than 60% of the rated working load should be applied to the upper sheave. Mount with 3mm x 6mm (1/4") fasteners (not supplied).Applications:Mainsheet and halyard applications, vang and spinnaker control lines on boats to 10m (33ft)S60 - on boats up to 12m (40ft)Materials:Alloy cheeks