Is the On Ultra Jacket fully waterproof?

On builds it with its GuardTec membrane, described as lightweight, breathable and waterproof. It is meant as a rain shell for running, not a heavy storm coat.

Can it pack into its own pocket?

On calls it a packable jacket, so it is meant to compress small enough for a running vest or pack. Check the product details for the exact packed size.

What weather is it made for?

Changeable and wet conditions on the trail, especially as an emergency layer during long runs and races. It adds little warmth on its own.

Does it work for ultras and races?

Yes, it is designed for ultra-distance trail running. Its low weight and packability suit kit lists that demand a waterproof layer.

How does it compare with other running shells?

It favors low weight and packability over pockets and adjustability. Rivals such as Salomon and Arc'teryx shells offer more features at higher weight.