Chain Pulley Block Spur Gear, Heavy duty alloy steel castings are used to make the load wheel.Gears are of alloy steel duly hardened for longer life.Heavy duty alloy steel castings are used to make the load wheel. Gears are of alloy steel duly hardened for longer life. Self-Sustaining: Has made the probability of a backlash non-existent enabling the load to remain suspended in times of accurate setting.Easy Lowering: This is delightfully smooth and easy. And owing to the absence of ratchet gear, is quite silent. Its perfect smoothness is a great factor in preserving the life of the chains.