Woolpower Thermal Short and Long Sleeve Undershirts Kingsbridge Supply offers Woolpower premium quality thermal tops that will keep you comfortable through a variety of weather conditions.  Choose from our selection of long underwear in short and long sleeve shirts from XS to XXXL.  The tops are made with Merino wool, a first-rate circular knit fabric designed to be worn as your base layer. These shirts have the incredible ability to wick moisture off your skin and keep you comfortable in temperatures well below 0 degrees F to 50 F.  Short sleeve shirts come in crew neck and long sleeve shirts are available in both turtleneck and crew neck options. Enjoy free shipping on all of our thermal tops.