Series 25 Ball Bearing Block

Ronstan Series 25 ball bearing orbit block with a 1 in (25 mm) sheave delivers a high strength-to-weight control-line solution for dinghies and small boats. The primary benefit is low friction and high load capacity in a compact package so your sheets and control lines run smoother under load.

When small boats need precise, reliable control but you must keep weight and size down, this block solves that trade-off. It is intended for mainsheet and spinnaker sheet turning blocks, cunninghams, cascading vangs and leech lines on boats up to 4 m (13 ft).

• 500 lb M.W.L. and 990 lb breaking load for verifiable strength under load
• Two-stage ball bearing system with high compression acetal sheave and balls for reduced friction
• Suits up to 8 mm (5/16 in) rope and accepts up to 4 mm (5/32 in) lashing through the hollow stainless steel hub
• Hollow hub with through-sheave becket take-off and swivel shackle head for flexible rigging options
• Frame of toughened glass fibre reinforced nylon keeps weight at 0.6 oz while maintaining durability

Compared to single-bearing or plain nylon blocks, the Series 25 offers faster line action and greater efficiency for competitive dinghy control systems where every gram and every millimetre of sheave matters. Use it where compact size and reliable bearing performance are required.

Materials and authority signals: toughened glass fibre reinforced nylon cheeks, high compression acetal sheave and balls, and a stainless steel hub. Manufacturer part RF28100. Designed for high-demand dinghy and small-boat applications and tested to the stated load figures; consult Ronstan technical data for racing class compliance. Learn more today.