Carbo AirBlocks® are 60% stronger and 30% lighter than Harken's Classic blocks. 

The nylon-resin sideplates are densely packed with long-glass fibers for a compact block with a high strength-to-weight ratio. Sheaves spin on high-load ball bearings with fitted races for low-friction operation. Ball bearings, sheave, and sideplates are UV-stabilized with carbon black for maximum protection.

Use 40 mm Carbo for jib and mainsheet systems on high-performance dinghies and for loaded control lines on small keelboats.

Use for:
Main/jib sheets
Mainsheet fine-tune
Control lines
Vangs
Cunninghams
Outhauls

Specs: 

• Max Line Diameter: 3/8"
• Sheave: 1-9/16"
• Safe Working Load: 485lb
• length: 3-3/8"
• Weight:1.6oz
• Shackle pin 4mm
• Breaking Strength: 1620lb