Spare parts including Spiked feet and Rubber feet including suction cups for your tripod legs.
Changing your tripod feet allows you to adapt to changing environments such as rocks, slippery surfaces, hard surfaces, ice and so on. The more appropriate the feet for the circumstances means a safer more stable and vibration free shooting opportunity.
Spiked feet for instance are best used on spongy and soft footings including damn grass. Spiked feet are also best used indoors on soft flooring such as thick carpet or rugs.
Rubber feet on the other hand are for hard and solid surfaces such as concrete pads, lookouts and paths. The rubber feet have a larger surface are than spikes and will provide more grip hence less movement.