The Seeland Heat jacket is made from a lined, lightweight fabric and has stretch membranes at the sides and on the sleeves for increased freedom of movement. Inside, it has a heat-reflecting lining that both prevents heat loss and enhances the effect of the jacket’s heating membranes. The collar is lined with a soft fleece. In the parts of the upper body most vulnerable to cold – between the back and lumbar region – there are heating membranes sewn in which, using a smartphone app, can be set to exactly the desired temperature between 30C and 52C. The membranes can also be set to 38C, 46C or 52C using the push button on the chest, without using the app, so you are not dependent on your smartphone. Unlike older heating technologies, the heating membranes are flexible enough to be folded up and packed away with the garment they are sewn into. The jacket can also be machine-washed with no problem. In the right-hand pocket of the jacket is a waterproof USB plug, so you can connect a power bank of your choice. With a power bank of 10,000mAh, the jacket can output its highest temperature of 52C for about 7 hours at an outdoor temperature of 0C. To save energy, the heat membranes automatically go into standby once the jacket has reached the set temperature. They then turn back on automatically if the temperature falls 1-2 degrees below the set level. The result is that the jacket is heat-regulating, because the heating function automatically turns off if you get hot from intense activity and turns back on when you are sitting or standing still. The jacket has two side pockets and an inner pocket and is supplied with a drybag to pack it away in.