These durable, secure screen covers are an effective and economical way to increase the versatility of your aquarium tanks by converting them for use as vivariums. Feature heavy-duty, impact-resistant, black frames with tough, corrosion-resistant mesh screening. Mesh allows total ventilation for maximum comfort for your animals. Covers are secured to the tank with two screw-lock mechanisms—preventing them from being pushed or bumped off. The two sizes listed are available with convenient, self-locking, sliding doors. Doors measure 5" x 6" and permit access without removing the cover. The 24" x 12" cover (without the door) will fit a 30-gallon River Tank.