A bit of history. A while back Rab introduced Boreas pull on jacket. Strechy, thin, breathable, providing some protection aginst elements, it was very successful as a light weather all-year-around
layer. Zephyr is a tougher version of Boreas adding abrasion resistent materials for the shoulder and arm. Still highly verstile. you can use it as an outer in spring, summer and fall. In winter, as a midlayer. Or as a protection for your expensive dawn jacket. Given the price, highly recommended.
This review was written in the old system and had content requirements that are different than reviews written today.