Standard size targets, the ones they charge 1$+ ea at the range for....

http://www.letargets.com/estylez_item.aspx?item=L-GA

15 cents ea. !

I buy a lot of stuff from these guys, and they always ship super fast..

They do have multiple styles, just check the clearance/special deals section....

They even have m4/m16 qual targets pretty cheap... for those with an ar that wan't 'real' targets...