From the folks who invented ball bearing blocks, this line of blocks boasts an excellent strength-to-weight ratio. The plastic in their sideplates, sheaves and balls makes them 30% lighter, 60% stronger and generally less expensive than equivalent conventional blocks.
Use the 40mmblocks for jib and mainsheet systems on high-performance dinghies, and for high-load control lines on small keelboats. The 40mmblocks handle loads similar to Harken's 2.25" blocks.