Ronstan's Series 40mm All 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.
This cheek block has stainless steel cheeks and 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. Requires 3x5mm (3/16 in.) fasteners.