Design is better than the one that does not lock, but the model is a tad too big. Also, the unnecessary edge at the right hand side (it locks in place, edge not needed) is in the way of having the mouse comfortable in the hand. This model needs some minor tweaks in my opinion. I had to "debur" all the edges of the locking extrusions just to get it to fit in my M575, and then had a very hard time removing the mouse from the mount afterwards because of the unpleasant edge.
In addition, a hole through the bottom and the plate to be able to turn off/press the connect button without removing the (hard to remove) mount would be a big plus.
