There are three things you can rely on once you ve laced up your running shoes a fast pace plenty of high-octane action - and your Jack Wolfskin Air Lock Jacket This innovative training jacket is extra warm weighs next to nothing and is exceptionally breathable In other words it s perfect for winter workouts Everything about this jacket is geared towards keeping weight to a minimum - including the ultra-lightweight PERTEX shell fabric and the innovative mesh fleece NANUK AIR LOCK Q M C consists of hollow fibres with a cross-section that looks like an eight-pointed star The advantage is it weighs less than regular fleece fabrics but provides better insulation The fabric s knitted-like structure makes it extremely breathable It is also air permeable Exactly what you need when you re trying to improve your PB on the fitness trail