Before: After: I've beet trying various poly mains since last October, including Lux, Sonic Pro, Focus Hex, and Turbotwist, and to various degrees have had quite a few arm issues cropping up, mostly minor. And about 5/6 weeks ago I put some string savers into a Turbotwist - Irradiated hybrid which stiffened it up dramatically and my shoulder started killing while serving. Unfortunately since more than a month of using Turbotwist - Spiral Flex (and frequent resting) hasn't gotten me to a point where I feel comfortable serving again, I decided that for whatever reason poly mains weren't for me and I wanted to try the most arm-friendly, spinny combination I could find. Gut. I'd tried gut twice before in the past: once in the mid 90s when I was a 3.5 and I really didn't notice anything different or special about it, and once about 2 years ago . . . when a stringer put in some that had way too much give and not nearly enough spin that I had them cut out after 2 hours(!). So thanks to some of the posts here at talk tennis, as well write ups about Fed and Djoker's setups, I was drawn to hybriding gut with poly crosses for spin. While I was initially leaning towards trying Silverstring crosses, two big shout-outs go to Tennis Warehouse University's string friction rankings and the posts of talk tennis member TimothyO for turning me towards MSV crosses in general and Co-Focus in particular. I'd wanted to start by trying a budget gut, figuring that if it was arm-friendly enough and at least comparable to Intellitour 17 (my personal reference string that I used for 7/8 years) then I'd be getting something that was good enough for my purposes and it didn't matter that the budget gut didn't perform nearly as well as VS. I couldn't get a set of budget gut quickly so I found Pacific Classic Gut 16g and pulled the trigger. Had it strung at 51 x 48. Initial Impressions My stringer notched it ever so slightly in a few places but nothing that appeared to go through the coating or seemed problematic. Just tapping the stringbed against the palm of my hand was a revelation: no vibrations going through to my racket arm, just proper contact feel. Felt great. I hit the court for an hour today doing moderate paced hitting with a friend who's a 3.5. The first 3-4 minutes were weird as it felt slippery and gloopy and biological, like hitting with a jellyfish. The ball pocketing and trampolining were like nothing I'd encountered before since I've used predominantly stiff(ish) feeling strings, and although I didn't notice any special spin being put on like with MSV Focus Hex, I sure noticed that more balls were dropping in and bouncing higher than expected. After 10-15 minutes I'd adjusted enough to it that I began to feel comfortable plowing through my groundies, especially my backhands. A few forays up to the net revealed very comfortable feel and placement, combined with almost effortless power. On my forehands especially, I noticed that I wasn't feeling any vibrations coming through to my arm anymore so I bit the bullet and tried a couple of serves --- slowly. Even without doing my full second serve motion, I immediately noticed the balls kicking up a good six feet high, about a foot higher than expected. My shoulder still wasn't ready to go full tilt, but this was clearly very promising. And the strings may still be a few hours away from settling in and hitting their stride. Specific Impressions String movement: none Spin potential: very good to excellent Power: good to very good Feel: very good to excellent Arm-friendliness: outstanding (Reference string: Intellitour 17g) I'll be playing at least a couple more times before next weekend with stronger partners who'll really put me through my paces, and I'll update then. And if anyone has any questions or items they'd like me to include in this review, please by all means ask.