The Rock Exotica Omni Blocks combine a swivel with a ball bearing pulley. These pulleys eliminate twisting and simplify your rope rigging system and save valuable vertical height compared to a conventional pulley/ carabiner/swivel combination. Each precision machined aerospace alloy block has a unique button-activated release feature that allows instant access to the sheave for midline attachment. The milled alloy attachment eye is large enough to accept most carabiners and snaps. 1.5 inch thread diameter pulley accepts up to 1/2 inch rope.