2 pin molex connector. 12v fan. Get one for cheap (I wouldn't pay more than $2.00) Find a PC at a thrift store, and give them $5.00. You should get a fan, the proper connector (from a 3.5 drive power cable), and a bigger external power supply for your GS as well. If you use a PC supply instead of the internal apple II supply, your IIgs will be much cooler inside