Gitzo GS5030VSF Video Rubber and Spike Feet, Set of 3

One foot, two states. The rubber cap threads in and out around a fixed spike, so winding it down covers the point for a studio floor and winding it up exposes the spike for grass. Nothing comes off and nothing gets lost in the grass, which is the failure mode of a pull-off cap on a night shoot.

They were designed for video tripods, where the same legs go from a hard stage to an outdoor location in a day, and photographers use them for the same reason. The set of three fits any Gitzo tripod with 3/8 inch removable feet and needs no adapter or tool to change over.