Ball bearing blocks deliver high performance and sensitivity for static and dynamic loads. A smooth and efficient block is critical to the conversation between sailor and boat—especially for hand-held control lines. Ronstan designed the Series 20 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, UV stable acetal sheave that runs smoothly on a two stage system of low friction bearings. Acetal ball bearings handle moderate loads for high efficiency. As forces increase ball bearings can become distorted; shy of distortion a plain acetal bearing running on a stainless steel race shoulders the load keeping the ball bearings safe from damage while maintaining low friction. 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 subtle messages your boat sends you though the lines by using efficient and smooth Ronstan series 20 blocks. This 20mm exit block is well suited passing halyards through masts, outhauls through booms or control lines through decks and bulkheads. Includes cover plate for a finished look to the installation. Key Features Light weight blocks designed for moderate to high static and dynamic loads Ideal for hand-held control lines Unique two stage bearing system: Acetal ball bearings deliver efficiency for moderate loads Sliding acetal bearing on stainless steel race handles high loads and maintains low friction Fiber reinforced nylon cheeks to add strength while reducing weight UV stable acetal sheave is strong and light-weight 316 stainless steel load straps add strength Ideal for: Halyard exits in masts Outhaul exits in booms Passing control lines through decks and bulkheads Ronstan Selection GuideSheave DiameterLine Compatibility20mm1/4" (6mm)30mm5/16" (8mm)40mm3/8" (10mm)50mm1/2" (12mm)