Pro-Ratchet 50Ratchet blocks feature an internal ratcheting mechanism which only allows the sheave to turn in one direction. This gives the user more control to make incremental adjustments to hand-held lines such as jib sheets, spinnaker sheets and mainsheets.Switchable - In the middle of the block is a switch that can be used, even under load, to turn the ratchet mechanism on or off. Giving you more control and feel of your control system. Extreme Hold - The Pro-Ratchet 50 features a hardwearing nylon sheave with eight V grips to give extreme holding power on all lines. For maximum performance, we recommend pairing this ratchet block with 7mm Excel Marstron Plus. Swivel Lock - The swivel can be locked in 90-degree orientations via the small black swivel lock at the top of the block. Alternatively, the swivel can be set to spin freely.Tii-Holes - The centre of the block features 4 holes to reduce weight as well as give options for tying elastic or rope through.