I have a 3" Astrosystems secondary holder with built in heater. THe heater has a "on" red LED and uses a little stereo headphone jack to recieve 12VDC. Comes with mirror but has a blemish on it and will probally need re coating. (Mirror is free) Asking $25 plus shipping. Selling because I downgraded to a 2.6" secondary for my scope. The string attached is a safety to keep the mirror from ever falling.