These are lids that fit 18x18x18 / 18x18x24 or 18x18x36″ Exo Terra terrariums, but please ensure yours are the newer Exo Terra with swivel clamps (2010 onward), not the spring-loaded push-in lids. Cheaper than you’ll find anywhere! Limited quantity WE DO NOT ACCEPT RETURNS ON THIS ITEM.If you have old model Exos, you’ll need to use a sharp razor blade to cut the tabs off of the top of your tank.