Be aware that heaters are probably the #1 piece of reef equipment to fail. When they do fail they have the ability to crash your tank at the same time. They are cheap enough to buy new as opposed to used. I'd rethink your decision to buy used heaters.
kenconnect, this is certainly not directed at you and your offer. Relz states in his title WTB: Heaters (plural), so he's apparently looking for more than one. Just a heads up.