what's a GOOD NMO mag mount??

I need some suggestions on a good mag mount !? I bought a Motorola mag mount off of ebay but it performs very terrible, I've tried 800/VHF/UHF and they're performing very little to nothing at all , so I returned it and I'm wondering what do you recommend for another mag mount to try???? I'm using it for a handheld scanner with a scanner antenna I have different and antennas for it



thanks in advance!