Rwo Nova Plain Bearing 38mm Single Block with Shackle Swivel Head Ai_Description 2 g Maximum Line 5

2 g Maximum Line  5 mm Maximum Working Load  125 kg  Breaking Load  450 kg

If you're between sizes or prefer a looser fit

Breaking Load  670 kg Fixing Hole Centres  57 mm Fixing Hole Diameter  4 mm Maximum Working Load  300 kg Sheave Diameter  25 mm Sheave Material  Alloy  Sheave Width  8 mm Slot Size  44 x 13 mm Weight 31 g

So you have one for each side of boat

Carbon reinforced ABS plastic construction with a stainless steel case back

Rwo Nova Plain Bearing 38mm Single Block with Shackle Swivel Head Ai_Description 2 g Maximum Line 5Series 38 plain bearing single open fork swivel block. Weight 59 g Sheave Diameter 38 mm Maximum Rope Size 10 mm Breaking Load 900 kg Work Load 450 kg