This black polycarbonate lid fits the shape of the internal vertical overflow boxes in Planet Aquarium tanks.

Exact measurements below. It's 1/4" thick polycarbonate, and will not warp like acrylic does. A customer ordered a lid and supplied the pictures you see of it installed, and he added those little feet you see. Those feet are not included. 

Lids are made to fit your overflow's dimensions, and there are a few sizes by Planet Aquarium. Please measure your overflow to determine what size your tank needs. Remember, I add 1/2" to all facing sides to cast a shadow over the teeth (see below):

Small: 13 3/8" x 6 1/2"  
Medium: 16 1/4" x 6 1/8"  
Large: 19" x 6 1/2" 

Also: 10 1/4" x 7"  for Crystalline 24" tanks - contact me to order

Special requests: Some customers have asked for a notch to allow for the light fixture clamp centered on the back of their aquarium. I can do this if you give me exact information. 

When I ship overflow lids, the protective film will be on both sides. Remove this film and put it into place.  The benefit of the lid:

• No algae grows inside the overflow box
• Less algae in the overflow teeth
• Keep livestock (fish and snails) out of the overflow area
• Bags floating during acclimation can't obstruct the teeth because the lid acts like a bumper, holding the bags 1/2" away from the gaps
• If you scratch it, you can flip it over to use the opposite side