"If you have Raynaud's or poor circulation, you know the dread of your fingers going ghost-white and dead numb from just grabbing cold groceries. This thing heats up literally the second you press the button. Wrapping both hands around the smooth curved aluminum brings feeling and blood flow back faster than running warm tap water. It never leaves my coat pocket."

 "Used these for three days skiing at Breckenridge. Anyone who skis knows freezing chairlifts drain your iPhone battery from 80% to dead in ten minutes. I kept this in my chest pocket—it kept my phone warm so the battery didn't freeze out, and when my fingers started stinging on the lift, I slipped it into my mittens for instant relief."

"The pebble shape is so comfortable to hold. It has a silky matte finish that doesn't slip, and it's small enough to drop right into a lightweight jacket pocket or purse without weighing you down. I use it on low for my 40-minute morning dog walks and only need to charge it about once a week."