Mycoal are a heat pack supplier based in the UK. Their heat packs are distributed across Europe and are invaluable supplies for outdoor enthusiasts. One Up Golf stock Mycoal Hand Warmers. They work by snapping the metal disk inside the pouch, which starts a chemical reaction causing the liquid to heat up. Hand warmers are ideal for defrosting your hands on a frosty morning on the golf course. Keeping your hands warm will help you to grip your club properly and play to your best ability.