I'm trying to buy these Power Slot rotors for the front and notice that the drop-down menu doesn't give you any specific vehicle option.

http://www.pfyc.com/pc/G64001/CBSUSP/Power+Slot+Brake+Rotors+-+05-07+G5%2C+G6%2C+Cobalt.html

How do I know I'm buying 5 lug rotors and not 4 lug? Are the 4 lug models the only ones to come with rear drum?