Allen Optimist Sprit BlockAllen Optimist Sprit Block. Featuring a ball bearing sheave which has been shaped to work with dyneema or wire. The flat side of the block is specially designed to sit against the mast of an optimist to stop any twisting, allowing the block to give the best lead for the sprit line and making it as easy as possible for the sailor to use whilst on the water. This Optimist hook will fit all Optimist masts and is 100% class legal.