Secures tightly, never loosens during use. I've had other plates that over the course of a day or assignment will loosen. This goes on and stays on, which means I leave a plate on both of my camera bodies as well as the support rings of my larger lenses. I really like being able to quickly attach to my PD tripod without having to fuss with tightening plates or attaching them beforehand. These just live on my gear, ready to use.
I wanted an extra standard plate for my second mirrorless camera body, to use with the Peak Design Capture. The plate can be left on my camera all the time since it also works as a quick release plate for my Arca-Swiss compatible tripod heads. Very convenient, and it's also small and low profile, so it feels like it's not even attached to the camera.
The purpose of this plate, as opposed to the standard Peak Design anchor mounts that come with the slide strap, is to allow mounting a camera or footed lens into an ARCA clamp without having to change mounts (from the ones included with the slide strap). The plate is indeed sized to fit an ARCA clamp, and has openings at all 4 corners.
Unfortunately, the positioning of these openings means the anchor strap is vulnerable to being compressed by the ARCA clamp. One must be very careful to avoid compressing and damaging the anchor strap. For the price, it should be better.