Fjallraven says about the Bergtagen Stretch Half Zip
When nothing is allowed to get between you and the summit, pull on your Bergtagen Stretch Half Zip. This durable climbing anorak is made from hardwearing four-way stretch fabric that gives maximum freedom of movement above the treeline. The design is deliberately simple so it doesn't interfere with your climbing harness or other equipment. Perfect as a tough, ventilating, weather-resistant work layer on spring and summer missions, and works well as a warm mid layer too.