Castelli creates the Insider Jersey specifically for the rigors of indoor training - situations in which cyclists exert maximum effort in areas with limited ventilation and air flow. To overcome these limitations Castelli creates knitwear from porous 3D Mesh fabric which allows air to move as freely as possible helping you stay cool whether you're banging around in the garage basement or stuffy bedroom. This airy material also wicks moisture better than traditional cycling jersey protecting against sweat and helping you stay dry and comfortable when you exercise. Despite the mesh design Castelli paid special attention to so that the insider T-shirt is not too transparent, which means that it would make a great outdoor tank for summer trips when temperatures approach triple digits and above.