Ronstan Ball Bearing 4mm Single Block RF40100

The Ronstan Ball Bearing 4mm Single Block RF40100 is a compact, lightweight single-sheave block designed for smooth, low-friction line handling across a range of marine rigging applications. Its two-stage ball bearing system delivers consistent performance throughout the working load range, with the sheave running on low-friction Acetal or Torlon ball bearings for efficient movement under load.

The Captive Lock universal head provides flexible mounting options and can be fixed in either of two planes or left free to swivel as required. Cheek cut-outs provide convenient access for bearing maintenance, while the slotted pin shackle is designed to help prevent lines from becoming fouled around the attachment point. The combination of low weight, efficient bearings, and versatile mounting makes the RF40100 well suited for compact rigging systems where smooth operation is important.