I have the Juggernaut Tactical AR-15 & 308 jigs, and the Modulus Arms HD AR-15 jig. The Modulus, with it's steel rather than aluminum plates, is superior by far. It's also billed as being compatible with multiple lowers. You'd think the Modulus would be a lot more expensive but it was only $179 while the JT's are $140ea. Can't wait for Modulus to come out with the steel 308 model.