Barton Marine Plain Block Double Swivel - Size 0Barton Marine Plain Block Double Swivel Size 0 The Barton Size 0 Plain bearing block has 20mm (3 4) sheaves and is also available in ball bearing sheaves. Designed for high strength and performance but lightweight with the range starting at only 13gms (0. 5oz). Suitable for up to 6mm (1 4) rope Ideal for use on dinghies, day boats and smaller craft or lead blocks, flag pennants etc. on larger yachts