Plain Sheave Single- swivel + becket New Meridian Zero 55 mm id the diameter

55 mm id the diameter of the D ring

The largest size can be attached using a 16mm line with a bullseye diameter of 28mm

This is an Official  RYA Publication

Evinrude Johnson OMC Engine Part COUPLING (3HP YACHT TWIN) 0205578 205578

NB  The boat is not at Putney so viewing by arrangement only

Plain Sheave Single- swivel + becket New Meridian Zero 55 mm id the diameterNew Barton Block Range Series 3: 45 mm Blocks A strong, lightweight range of blocks for use on dinghies, day boats and light cruising yachts. Ideal for mainsheet, vang, lead blocks or wherever a powerful and compact purchase tackle is required. A comprehensive range of cam cleat, fiddle and fiddle & cam cleat versions are available. Plain bearing blocks Barton plain bearing blocks have a precision moulded acetal sheave running on a large diameter