The red thing
Sorry should have explained - that is a foundry pattern when the casting is machined it can take different legs. The one I cant find is the multi adjustable one that has Ex post office "Centre" bubbles in each leg to maintain all legs level. The rest takes the rifle stock and clamps in position. The one shown is a basic - one I used for sighting in with as well as using it at Aldersley Stadium Wolverhampton on the Bench rest air-rifle range back in the early 1990's.
One of the sand bags is in the boot of my car at the moment.
I will have to check up on the rules as they have more than likely changed since I last shot bench rest back in 1994.