General application blocks provide performance and value. A smooth and efficient block is critical to the conversation between sailor and boat—especially for hand-held control lines. Ronstan designed the Series 50 All-Purpose blocks to give dinghy and small keelboat sailors the feedback to detect subtle wind changes and sail as efficiently as possible. These light-weight blocks feature a durable, self-lubricating, UV stable acetal sheave that runs smoothly on a 316 stainless steel bearing. Fiber reinforced nylon cheeks provide rigidity and strength and are beefed up 316 stainless steel load straps. The included shackle features a pin with a low-profile head to prevent snagging on smaller lines. Get the messages your boat sends you though the lines by using efficient and smooth Ronstan Series 50 All-Purpose blocks. This 50mm single with shackle head is versatile and can be used for a wide range of applications. Great for halyard tuners, Cunninghams, dinghy sheets and more. Key Features Light weight blocks designed for moderate to high static and dynamic loads Ideal for hand-held control lines Captive lock secures swivel at 0 or 90 or left to swivel freely Sliding acetal bearing on 316 stainless steel race handles high loads and maintains low friction Fiber reinforced nylon cheeks to add strength while reducing weight Self-lubricating, UV stable acetal sheave is strong and light-weight 316 stainless steel load straps add strength Ideal for: Dinghy and small keelboat sheets Halyard tuning systems Backstay systems on dinghies and smaller keelboats Boom vangs (cascade systems) Ronstan Selection GuideSheave DiameterLine CompatibilityShackle Pin Diameter20mm1/4" (6mm)1/8"30mm5/16" (8mm)5/32"40mm3/8" (10mm)3/16"50mm1/2" (12mm)3/16" (1/4" for Double and Triple blocks)