This glass cover is designed for DOOA NEO Glass Air small terrarium/aquarium. The glass cover covers the entire Neo Glass aquarium.  The glass cover comes with 4 small transparent anti slip pads that sits on the four corners.  The pads raise the glass cover slightly from the aquarium, allowing air to go into the slit in between the glass cover and the aquarium for circulation.  The pads also allow adjustment of an opening from the top by simply sliding the glass cover to create a gap of your desired width.