Rab mens alpha flux jacket the mens alpha flux jacket is a highly breathable lightly insulated outer or mid layer that uses polartec alpha tm direct technology and stretch fleece for on the move multi season use the mens alpha flux jacket is shelled in a new super soft yet durable woven outer fabric which has a high level of air permeability this is paired with our thermic lux tm light stretch fleece in strategic areas of the body to allow freedom of movement and to reduce bulk