Grade 316 stainless steel sheaves running on needle roller bearings deliver low friction performance and a long service life. An extra wide stainless steel frame extends to the full diameter of the sheave to prevent lines from becoming jammed between the sheave and cheeks. Sheaves are removable for easy maintenance and can be used with rope or wire. Trunnion snap shackles are standard for maximum articulation. An attachment point is provided for a shock cord retainer to hang the block from the lifelines.