Harken 29mm Wire Cheek Bullet Block,

Low-friction Bullet blocks lead control lines aft. They are compact and lightweight, with fast trim and release under high or low loads. A range of styles lets these blocks adapt to almost all control line applications. Wire Bullet blocks use roller bearings to carry higher loads and feature hardcoat-anodized PTFE impregnated aluminum sheaves for strength and corrosion resistance.

Harken 109