Keyguard for the original Apple Magic Keyboard for iPad.  This is not the Magic Keyboard for the Mac, and it's not the Apple Smart Keyboard, and it is not the current model of the Magic Keyboard.  It's the original Magic Keyboard for iPad that worked with the 12.9 Pro 2nd Generation, and perhaps later for the iPad Air 4 10.9.  It is distinguished by its smaller, more rounded key caps.  See the pictures to be sure it's the one you want.

The default material is 3/16" clear acrylic.  1/8" high-impact PMMA is available for users who require the openings to be shallower, but is not recommended, since it is more flexible and may become warped or dislodged. There are also a number of 1/4" thick materials available.

No attachment method is provided with this keyguard.  You'll need to attach it yourself with something like double-sided tape, Velcro, or mounting putty (Blu Tack, etc.)