Two jackets, three different weather situations - triclimate jackets are based on the original mountain layering system and, as such, are really versatile. For the ThermoBall Eco Triclimate Jacket, we've combined a waterproof, windproof and breathable 2.5-layer DryVent shell with a recycled polyester insulation layer. What's so special about that? The ThermoBall Eco insulation maintains its warmth even when wet, making it the perfect partner to a waterproof shell. Wear them together on days when the weather really tests your resolve. On cold but dry days, you can wear the ThermoBall insulation on its own. When it's wet, blustery and mild, opt for just the DryVent shell. The shell is made using stretchy fabric and it has underarm vents, so you can keep it on and stay comfortable even when you're charging up hill in a downpour.