This is great for the forward mainsheet block and upper block with clip for attaching to the boom bridle on the Optimist. Ball Bearing Orbit Blocks™ boast the highest strength-to-weight ratio available. This is achieved through all-composite reinforced polymer materials and multiple attachment options. Their precision design provides the optimum number of ball bearings for minimum friction while weight reduction is achieved through the use of fibre-reinforced composites in the block head, cleat arms and beckets. Features: Sheave Dia.: 1-3/16" (30mm) Pin Diameter 5/32" (4mm) Max. Rope: 5/16" (8mm) Maximum Working Load: 300kg Breaking Load: 600kg Single block Swivel shackle head Lightweight Highest working load in its class Secure, versatile and secure attachement Low profile and compact Ultra low profile thru-sheave becket. Low friction 2-stage ball bearing system provides consistent performance over the full working load range. Materials: Sheave: High compression strength carbon black Acetal Ball Bearings: High compression strength Acetal Frame/Cheeks: Toughened, glass fibre reinforced Nylon Link: UV stabilised, multi-strand impregnated SK75 Dyneema® Availability: Usually ships the next business day. RF35100Regular price: $20.95Sale price: $15.99 Due to the wide variety of the size and weight of our items we will charge the actual cost of shipping in a separate charge on all orders. Please email us for a shipping cost estimate. Shipments outside the USA may have add on fees and duties by your own government. Sailing can be green! See our recycle your old sail offer Send us email