Quite an expensive additional piece of hardware for what is quite a cheap rack, this sheet of glass itself is of good quality, but the hardware that comes with it is fairly poor. It's difficult to install into an existing rack as it's possible your rack isn't perfectly square, so you'd better install it from the beginning, but it's raises the price of a cheap rack significantly.
Sadly the "lock" is a joke. The cam on the lock doesn't engage properly with the supplied hardware, so once the door is "locked" you can simply push it a little bit and it will slide past. Barely 1mm of metal is caught by the latch. Since the hinges snap into place when the door closes (which is quite nice), the lock should just be replaced with a handle. I didn't expect it to be a "security" feature, and the glass door was more for protection accidental bumps and dust for my situation, but having useless, cheap feeling, so-called "lock" rather than an actual handle just cheapens the rack further.
I'd usually say you get what you pay for, but given the price, this one really hurt.