A chock works by presenting a face to the tyre at the right angle, so wheel diameter matters as much as the rated capacity. A chock sized for a car tyre against a truck wheel simply rolls out of the way, which is why a chock for wheels larger than 920mm diameter is listed separately. Getting the angle wrong is a failure that only shows when the vehicle actually starts to move.
Capacity is quoted per pair on most of the range and per chock on the heavier singles, running 2 tonne to 10 tonne. Chocks are used in pairs on opposite sides of the same wheel, or across both wheels of an axle, so the pair figure is the one that usually applies.
Material changes how the chock behaves rather than how much it holds. Rubber grips the ground and the tyre and stays put on a smooth floor. Plastic is lighter to carry and to place, which matters where chocks are moved constantly rather than left in position. Heavy duty rubber forms sit above the standard pairs at the same capacity with more material behind the face.
Commercial forms add a bracket so the chock is stored on the vehicle rather than left behind, and motorcycle chocks work differently again, holding the front or rear wheel upright in a trailer or a bay rather than stopping a vehicle rolling. Questions go over WhatsApp on 07754288583 with the wheel size.