Series 25 Ball Bearing Block

The Series 25 Ball Bearing Orbit Block is a 1in (25mm) single-sheave ball bearing block with becket and lashing head designed to give you high strength and low weight for dinghy and small-boat control lines. Its primary benefit is reduced friction under load thanks to a two-stage ball bearing system built for control-line tasks.

Problem: high friction and heavy hardware slow sail handling on small boats. Solution: this block uses a high-compression acetal sheave and ball set with a stainless steel hollow hub to lower friction and permit efficient becket take-off or secure lashing attachments up to 4mm.

• Two-stage ball bearing system reduces friction for smoother sheet handling
• Sheave 1in (25mm) suits lines up to 8mm (5/16)
• Hollow stainless steel hub accepts becket and up to 4mm (5/32) lashing
• Breaking load 1650 lb and weight 0.5 oz for high strength-to-weight ratio
• Frame of glass-fiber-reinforced nylon for durability in marine conditions

Use cases include mainsheet and spinnaker sheet turning blocks, cunninghams, cascading vangs and leech control on dinghies to 4m (13ft). Compared to plain nylon plain-bearing blocks, this ball-bearing orbit block lowers start-up friction and maintains performance under repeated loading.

Materials and authority: acetal sheave and balls, toughened glass-fiber-reinforced nylon cheeks, and a stainless steel hub. Manufactured by Ronstan MPN RF28109 and specified with a 1650 lb breaking load. Choose this block when you need measurable friction reduction and a compact lashing-ready attachment. Learn more today.