Macscale
Aquarium Advice Addict
Not sure how deep they penetrate but the kessil 150w's cover 24"x24" I believe. Maybe some one who uses kessils can confirm (*cough* Bribo *cough* )
Pretty sure it is a 24"x 24" x 24" cube. All I've ever found was it penetrates deeper then your tank. Not pertaining to you specifically but just a phrase.