The 18 mm block features stainless steel ball bearings and an integrated stainless inner race and rivet for optimal strength-to-weight. The 40 mm blocks feature composite sheaves that spin freely on Delrin ball bearings with curved bearing races. They have no metal shackles or rivets, making them the lightest soft-attach blocks Harken has ever designed.

Delrin is a registered trademark of E. I. du Pont de Nemours and Company or its affiliates.