The 40mm Carbo works well if mounted on the bow pulpit as an inboard lead. The 57mm Ratchet maintains tension while spooling. The 40mm and 57mm have ball and socket bases to align blocks for smooth leads aft. The Lead Block Kit contains a complete system for most boats including 3 29mm Outboard Lead Blocks Assembly, 1 57mm Carbo Ratchet Lead Assembly, 1 40mm Carbo Lead Block Assembly and 1 Cleat. Lightweight, UV stabilized Carbo blocks run on ball bearing sheaves for fast trimming under load.