A couple of years ago I was doing some late season BP hunting and the temp. was getting to30 below while I was out.I couldn'tget enough layers or warmers in the boots orgloves to keep me going very long on the stand. I read a tip on here that waslike shaggys, except instead of the middle of your shoulder blades, tape one heat pack over your tee shirt overeach kidney area on your back. I couldn't believe the diff. it made.My toes didn't even get cold, and that never happens.