Ronstan RF15101 Series 15 Ball Bearing Block Single Loop Top

The Ronstan Series 15 Ball Bearing Single Block is an ultra-compact, lightweight block featuring a 5/8" diameter sheave with exceptional strength-to-weight ratio. This micro block delivers ball bearing performance in the smallest package available, making it ideal for dinghies, small sailboats, and creative rigging applications.

Key Features:

• Precision-molded UV-stabilized acetal sheave running on stainless steel ball bearings for smooth, low-friction operation
• 316 grade stainless steel cheeks, headpost, shackle, and ball bearings for maximum corrosion resistance in marine environments
• Single loop head design with O-ring separator to prevent interference between running line and attachment hardware
• Smallest and lightest ball bearing block on the market at just 0.3 oz (7 g)
• Versatile applications including cunninghams, vangs, tweakers, shock cord retractors, and purchase systems
• Ideal for youth sailing classes (Optimist, El Toro, Sabot) and high-performance dinghies

Specifications:

• Sheave Diameter: 5/8" (15 mm)
• Maximum Line Diameter: 3/16" (5 mm)
• Maximum Working Load: 260 lbs (120 kg)
• Breaking Load: 1,210 lbs (550 kg)
• Weight: 0.3 oz (7 g)

Perfect for sailors looking to reduce weight and add efficient mechanical advantage in space-constrained applications. The combination of ball bearing technology and micro dimensions makes this block suitable for both marine and land-based rigging projects.