These are Crane Hook Blocks / Bottom Blocks with swivel hooks
What they’re used for:
These are used on cranes, hoists, and winches to lift heavy loads. The hook connects to slings/chains, and the sheave/pulley wheel at the bottom guides the wire rope.
Key details from the photo:
1. Capacity: The yellow block is marked 10000 KG = 10 Ton capacity
2. Hook: Black forged steel swivel hook with a safety latch to prevent slings from falling off
3. Sheave Housing: Yellow with black stripes - for high visibility on site. Still wrapped in plastic so they look new
4. Type: Single sheave block - meant for 1 part of wire rope