The AP-609 Quick Release Replacement Foot for Sony: 400 f/2.8 GM OSS from Wimberley is an anodized 6061 aluminum plate that is Arca-type compatible for use with most clamps and heads on the market. By replacing the original factory foot, the AP-609 adds rigidness and stability and reduces flex and vibration while mounted on a head. 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.
UPC: 753182834818