Ronstan RF56510 Series 55 Ratchet Mount Orbit Block Fiddle Becket Swivel

The Ronstan Series 55 Ratchet Mount Orbit Block is a high-performance fiddle block with becket and swivel designed for sailboat mainsheet and jib sheet systems. This innovative block features dual-mode ratchet engagement—automatic mode engages under load and releases when tension is removed for smooth sheet easing and rapid asymmetric spinnaker gybing, while manual mode allows on-demand ratchet control preferred by competitive sailors.

Key Features:

• Up to 20:1 holding power with patented Generation 2 sheave geometry
• Dual engagement modes: automatic load-sensing or manual on/off control
• 12 gripping faces with straight resistance for optimal load distribution and minimal rope wear
• Smooth, controlled sheet easing in automatic mode
• NC-machined sheave with cross-hole design draws rope into gripping area under load
• Fiddle block configuration with becket and swivel for versatile rigging options

Construction:

• Sheave: Hard-anodized aluminum for durability and corrosion resistance
• Ball bearings: High compression strength carbon black acetal for smooth operation
• Frame and cheeks: Toughened, glass fiber reinforced nylon composite
• Rope link: UV-stabilized multi-strand SK75 Dyneema® for superior strength-to-weight ratio

Ronstan Ratchet Orbit Blocks deliver the highest holding power available in their class, nearly double that of competing designs. The offset gripping faces provide straight resistance rather than angled resistance, reducing rope wear while maximizing control. Ideal for mainsheet systems, jib sheet controls, and high-load applications where precise control and exceptional holding power are essential.