UNIHAND hand warmers: questions and answers

Charge both units fully indoors with the USB-⁠C cable packed in the box. Then press the orange button to switch one on and count the red lights to see the level. The card in the box gives the exact presses, and our instructions page walks through every step.

Hold them back to back, the way the pebble shape invites. The two become one warmer about the size of your palm, warm on every side. Switch both on first, at the level you want, and pull them apart again whenever you need two separate warmers.

A USB-⁠C cable, and one comes in the box. Plug its other end into a USB charger or a computer port. Charge one unit at a time with the cable you have, or use a second USB-⁠C cable of your own to charge both at once.

We give no fixed charge time for the pair. Leave it on the cable until the lights show a full battery, and charge at room temperature. Partial top-ups between outings do no harm to a lithium-ion battery.

Count the red lights beside the orange button. One means Low at 95-⁠107.5 °F, two means Medium at 104-⁠118.5 °F, and three means High at 118.5-⁠130 °F. Blue lights you may see belong to the battery and heating status display.

Twenty hours is our ceiling for one unit on Low. Cold air drains a lithium battery faster, wind pulls heat from the shell, and each time you switch on costs a little. High uses the battery fastest of the three. Our heat levels page explains the trade.

No. On High a unit reaches 130 °F, and a hand warmer is no plaything. Young children may not tell you when something feels too hot. If a child carries one, an adult sets the level, keeps it low, and checks the child's hand now and then.

Talk to your doctor first. Skin that cannot feel heat well can burn without warning you. The NIDDK says nerve damage from diabetes can make it hard to sense temperature in the hands. A warmer is not a treatment for numbness, circulation problems or any medical condition.

Stop using it straight away and unplug it. Move it onto a hard surface away from fabric, paper or anything else that could catch, and keep it off the charger for good. The Battery Network says swollen or overheating batteries need special packaging before recycling.

The FAA lets a lithium device ride in a checked bag only if it is fully switched off and cannot be turned on by accident. It would rather see such batteries in the cabin, where crews can deal with one that overheats. Put the pair in your carry-on.

Wipe the shell with a soft, dry cloth after each wet or snowy day. Never rinse a unit or soak it, since the pair has no water rating. If a warmer did get damp, leave it switched off until it is completely dry, and only then put it on the cable.

Store both units somewhere cool, part charged rather than full or empty. Battery University suggests about 40 percent charge and around 59 °F for lithium-ion storage. Avoid a hot car or a sunny shelf, and give each unit a full charge before the first cold week.

It suits anyone who spends part of the winter waiting in the cold, from commuters to golfers, hunters and stadium fans. Two warmers in one box means one present can warm two people. Charge it before you wrap it, so it works the evening it is opened.

Ten: Black, White, Champagne, Bronze, Pink, Purple, Sky Blue, Mint Green, Dark Green and Blue Grey. Both warmers in a box share one color, and every color works the same way. You can see the full set in our hand warmers collection.

Two rechargeable hand warmers of the same color and one USB-⁠C charging cable. A card in the box shows the button presses. You supply the USB charger for the wall, the car or a laptop port.

Write to us through our contact page, where you will find our email address. Tell us which color you have and what happened, and we will reply by email. Questions about payment or delivery belong with the partner where you placed the order.