PAIR Tuphblox Fiddle Blocks - 3/8" LinePAIR Tuphblox Fiddle Blocks 3 8" Line. The regular fiddle block has a 2 3 8" and 1 1 2" sheaves. This is a fixed block but has the top area for mounting a shackle in either direction. The fiddle with cam cleat both sheaves are 2" diameter. The cam cleat does get stuck open some but has a 13 16" width fully open. This block is 9 1 2" total length including the shackle.