Ronstan Series 55 Single Becket Swivel Orbit Block

The Ronstan Series 55 Single Becket Swivel Orbit Block is designed for mainsheets, spinnaker sheets, halyards, vangs, and backstays where a compact single block needs its own standing-end attachment. The becket keeps the fixed end of a purchase on the same assembly instead of requiring a separate deck fitting. A swiveling head lets the block align with changing load direction, which is useful in tackles that move as the sail is trimmed. Ronstan recommends this size for dinghies, sportsboats, and small keelboats in the applications covered by its published load limits.

The Orbit bearing system uses high-compression Acetal ball bearings with a secondary carbon-fiber reinforced, PTFE-impregnated nylon bearing surface. That two-stage arrangement keeps the sheave free-running under lighter trimming loads while still supporting it as the load rises. A Dyneema link and lightweight composite structure help keep overall mass down without turning the block into disposable race hardware. The result is a low-profile block that suits active sail controls as well as more permanent rigging layouts.

• Integrated becket for the standing end of a purchase
• Two-stage Orbit bearing system
• Swiveling attachment follows changing line angles
• Low-profile construction for compact rigging

This model accepts line up to 10mm (3/8 in), carries a 1,100 lb maximum working load, and has a 2,200 lb breaking load. Its published weight is about 3.1 oz, which is useful when minimizing moving weight in running rigging. Lay out the becket, swivel, and rope lead as one complete system so the block is not pulled sideways at full load. For related Orbit blocks, beckets, and sail-control hardware, browse more Sailing Hardware.