Consists of two 29mm Carbo T2 blocks spliced 8 in apart with Amsteel Blue Dyneema. No shackles or rings needed. Just luggage tag them on to your jib. Harken Carbo AirBlocks are lightweight, strong and reliable. Sideplates of high-strength engineering resin are UV stabilized to provide excellent protection against long-term exposure to salt water and sun. The low profile T2 replaces stainless headpost, shackle and spring with high-tech line.