I use GHS Pressurewounds on my 'Rays. I've previously used Chromes and Super Bright Nickels. Honestly they all sounded good but the Pressurewounds really hit a homerun for me. RATM's bass tone has more to do with Commeford's effect chain and amplification than his string choice in my opinion. I'm pretty sure he uses or used Ernie Ball Slinkys on his Ray's though.