its open in the back for cords, overflows, whatever
the whole thing sits on 4 lil blocks.. 1 at each corner...
the inside is sealed with silicone which i painted on with my hands and a creditcard.. paint first THEN seal...
make sure you take into account the hight of your lights or you will end up rebuilding it... either way its best to make it taller than you "think" it needs to be.. i just changes my lights to one 48" fixture... its 5/8 of an inch taller... i only left 1/2 an inch of space... so now i have to make another one or remake the housing for the lights.. im not sure which is more of a pain in the butt..
the sides are 4.75" so with the top its 5.5"... front flip up piece is 3.75"
i think i decided that im just going to move the 4 small blocks that rest on the tank... which will expose the trim.... which will look like crap...... gah...