right now i have 24 hr and 72 hr they are activated by oxygen they get to about 110 at peak then run about 95 deg there after they run all sorts of different prices i think i got a good deal at 2.00 per pack i only have a few more 72 hrs left. work good but you have to be careful how to pack your box. they are used a lot in mailing reptiles and fish i could not believe that but they must do it.
mike
