Ronstan Series 40 Ball Bearing Cheek Orbit Block

The Ronstan Series 40 Ball Bearing Cheek Orbit Block is intended for fixed turning points where the rope needs to stay close to a deck, mast, or boom. Its cheek-mounted layout saves vertical space and avoids the movement of a swivel head when the line direction is already known. Ronstan's Series 40 Orbit family is used for mainsheet, spinnaker, halyard, vang, and backstay controls on performance dinghies, catamarans, and sportsboats. This version suits installations where a compact, low-profile change of direction matters more than articulation.

A two-stage bearing system combines free-running ball bearings with a secondary support surface that takes load as tension rises. The cheeks are toughened glass-fiber reinforced nylon, reducing weight while still protecting the sheave in exposed deck service. Because the block is fixed to the mounting surface, careful alignment lets the bearing system do its job without unnecessary cheek friction. The simple cheek layout also leaves the rope groove easy to inspect when the line is removed for seasonal service.

• Low-profile cheek-mounted turning block
• Two-stage Orbit ball-bearing system
• Glass-fiber reinforced nylon cheeks
• Fixed mounting keeps the rope close to the surface

Ronstan rates this model for line up to 3/8 in, with an 880 lb maximum working load and a 1,760 lb breaking load. Its published weight is about 1.2 oz, making it well suited to weight-conscious spar and deck installations. Set the mounting angle before drilling so the incoming and outgoing rope remain centered on the sheave through the full range of use. For more cheek blocks and low-profile sailing hardware, browse more Sailing Hardware.