This thing is was made to hold a laptop, 2 iPads, and a keyboard or Kindle.

Opening are 35mm, 20mm, 15mm, and 15mm. Each slot was designed to have a little extra room for my devices, but snug enough to keep everything slightly leaning back to protect the face/screens.

The 35mm should be enough space for most modern laptops. The 20mm fits an iPad Pro with the official keyboard case. The 15mm fits and old iPad Air, a Kindle, or the iMac Keyboard.

There are larger braces on the back because of the potential for a heavy laptop to press against the back of the stand. Small braces on the front.