there is diff sizes.. just make sure to get a hps.. also i think the 50watt may to nicely in the little pc tower.. u may have to remove the outer shell and just leave the silver backing intact.. 6" x 6" x 6" but if able to remove shell i would say mmay b 4"ish thick.. u could always mount on the top of the cpu and mount it looking down in.. but just my input! good luck.. and hope that helps your yield... may want to grow like 6 little pots in there too get the best yield for all u troubles.. peace