Velocity DT Jacket.
Montane call this The world's lightest weight, waterproof and breathable cycling jacket and at 220 grams they might not be far wrong.

Designed for the high-energy cyclist who demands dependable design and ultra low weight in a fully waterproof shell.
Feature rich, with 3M Scotchlite reflective detail, a cycle sport-active cut, roll-up venting sleeve forearms, a micro-fleece lined and cinchable collar and two vented pockets, this is no stripped down racer.
The Velocity DT is what fast and light bikers have been wanting for years, a waterproof that packs smaller and lighter than the average toolkit and weighs less than half that of most other ‘lightweight’ jackets available.

Features:
Cycle sport specific active cut with pre-bent, extra-length arms and drop tail.
Two MONTANE® part-vent zipped chest pockets with storm flaps.
DWR Beardguard lined collar.
Full length two-way zip with storm baffle.
Part elasticated hook and loop adjustable cuffs.
3M Scotchlite reflective strips.
Hook and loop adjustable collar.
Single hand adjustable, elasticated draw-cord hem.
Attachable Stuff sac.
Weight 220g / 8oz: (Medium size)