Tapered roller bearing, NSK 52400/52618. Three in stock.
I’ve had these for over 10 years and never got around to doing anything with them. Originally bought from an army surplus store. 
In good condition but with minor spots of surface rust. Turns well, nice and solid.
Dimensions:
Outer diameter: 155mm (6 1/8”)
Inner diameter: 100mm (4”)
Depth 1: 35mm (1 5/8”)
Depth 2: 25mm (1”)
Weight: 2.5kg