These quick releases are excellent. They operate similar to the old Canon breech lock lens mounts, which is a good thing. Apparently they are very similar to units from Arca. I have these Leofoto quick releases in a couple sizes (QS-50 and QS-60), and they work really well for quick connect or disconnect of tripod heads from tripods or other accessory arms that go on tripods (such as the Leofoto Multi-Function Arm). I have other click-on-and-off quick releases for larger tripod heads, but those click-style quick releases use multiple parts which potentially could fail, and those other units are larger and stick out and would get in the way in certain applications. So when you want to have the ability to quickly remove tripod heads from tripods or monopods or other similar accessories, and if you want something that doesn't stick out and can be obtained in a size that fits closely to your application (such as to match the diameter of your tripod head mounting surface or monopod mounting surface or the mounting surface on a horizonal arm accessory for your tripod), these Leofoto QS units are the way to go. They're easy to operate, and there's almost nothing about them thats likely to fail, and they lock securely, and they don't seem like there's any chance that a tripod head with a camera could come off accidentally. And like the other Leofoto items that I've purchased, these things are high quality. I'm always amazed when I buy another Leofoto product how nicely made this stuff is. And its always well-packaged, which shows me that they have a lot of attention to detail.
