Review on Kori Cryosphere Cold Massage Roller Ball: 6-Hour Cold/Hot Relief, Rapid Recovery, Inflammation Reduction – Removable Ball, Ice Roller, and Myofascial Release – Perfect Massage Gifts by Bethany Neal

I have just recovered from sciatica and have found this helpful and soothing. It feels cool even after prolonged use. I didn't try it frozen but I tried it hot and it was lovely and stayed warm for a long time. I would say it stayed warm enough to use for over an hour and was still noticeably warm 3 hours after use. After my stretches, I would roll it over the entire area. I also found it very helpful to take it out of its holder and sit on it to relieve various pressure points along the sciatic nerve that were the most painful. It glides rather than rolls over your clothes. It rolls a little, but not if you have to push it hard. Still works great.