These are really good (3 pack) cold packs, each coming with a clear plastic sleeve) which you can either pop into the freezer, heat up in a pad of hot water, or (if not frozen) pop in a microwave.
I found that these gel packs stay cold for so much longer than any I have had in the past ... so much so, that long after you have started to get some relief, if you take the pack off you can still see a frosty condensate.
You really do need to wrap these packs up in a tea towel or towel as putting them straight on skin may cause freezer burn. depending on the area affected, I find using a bit of old tubeygrip (tubed leg bandage) will give you enough tie on and secure.
When taking the packs straight out of the freezer they can be a little stiff, but with a bit of careful working for a minute or two, can be made malleable enough to wrap around a wrist or ankle.
In summary, these are the best cold packs I have ever had, and buying them in packs of 3 means that you will always have a spare if you need to use more than one.
To be honest, even after half an hour the packs remain surprisingly cold. Very Good