Designed for the Canon EF 400mm f/2.8L IS III USM lens, the AP-601 Quick Release Replacement Foot from Wimberley is an anodized 6061 aluminum foot that is Arca-type compatible for use with most clamps and heads on the market. By replacing the original factory foot, the AP-601 adds rigidness and stability and reduces flex and vibration while mounted on a head. Additionally, a double dovetail allows accessories to attach to the bottom or the top of the foot. The lower profile of the plate provides better balance when mounted on a head as well. If you're going to use the optional safety stop screws, Wimberley recommends using a clamp with channels, which allow the screws on the foot to slide back-and-forth.