Harken carbo 57mm ratchet block 4sh, its the perfect lower block for the 1:08 system. The Carbo Ratchamatic® is a load-sensing ratchet block that rolls freely in both directions under low loads. For example, the blocks automatically engages the ratchet as loads increase. Shifting between ratchet and light-air modes is seamless.
The 1:08 system is most used on the Nacra’s 460, 500, 570, F16 and F18’s.