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Mountain Equipment says:
Warm, breathable and exceptionally comfortable; the perfect mountain layer for everything from the most difficult alpine climbing to ski-touring and hiking.
With a lightweight, air-permeable stretch shell and breathable POLARLOFT® synthetic insulation the Transition strikes the perfect balance between warmth, comfort and mobility for any stop-start mountain activity. Comfortable worn alone through a range of conditions it becomes the ideal mid-layer in the most severe weather.