Ronstan Series 30 Triple Ball Bearing Orbit Block

The Ronstan Series 30 Triple Ball Bearing Orbit Block packs three low-friction sheaves into a lightweight block for dinghy mainsheets, spinnaker sheets, halyards, vangs, and backstays. Its triple layout lets a rigger build useful mechanical advantage without hanging several separate blocks from the same moving point. Ronstan recommends the Series 30 Orbit range for sheet systems on dinghies to about 5m (16 ft), with the same size also suited to several control-line applications on boats in that range. The compact profile is especially useful where weight and stack height matter.

High-compression Acetal ball bearings support the sheaves, while a secondary bearing surface carries additional load as line tension increases. The reinforced load frame avoids the weight of a conventional full stainless strap and keeps the block easy to handle in small-boat running rigging. An SK75 Dyneema link provides a light, flexible attachment that lets the block align naturally with the purchase. Together, those features give the block the quick response expected from a performance-oriented dinghy control system.

• Triple-sheave layout for compact mechanical advantage
• Two-stage low-friction bearing arrangement
• Lightweight reinforced load frame
• SK75 Dyneema attachment link

This block accepts line up to 8mm (5/16 in) and carries a published maximum working load of 1,210 lb. Ronstan gives the breaking load as 2,430 lb and the block weight as about 2.6 oz. Reeve all three sheaves so the rope parts remain parallel and the soft link is free to align with the load. For more lightweight multi-sheave blocks and dinghy rigging, browse more Sailing Hardware.