From the Patagonia Website:
There's a difference between going light and being unprepared. Weighing in at a featherweight 6.5 ounces, the waterproof/breathable Specter Pullover has a stitch-free seam construction (our Composite Seam System„¢ technology) that minimizes weight and bulk as well as improves wet-weather performance and durability. Technical, minimalist detailing includes coated zippers, a helmet-compatible, roll-down adjustable hood and a deep front zipper for ventilation and easy on/off. The main zipper is offset at the chin in the opposite direction of those found on Regulator® insulation tops for layering comfort. The pullover stuffs into its own internal zippered mesh pocket, and a clip-in loop keeps it handy when the skies unleash. With a reflective heat-transfer logo. Sized to pull over layers.
Lightweight fabric and the Composite Seam System„¢ technology combine to make the Specter ultra light while improving wet weather performance, durability, softness and compressibility (patent pending)
Interior surface texture channels moisture away from skin, protects the waterproof barrier from abrasion and slides easily over layers
Helmet-compatible, two-way adjustable hood with soft cordlocks integrated in the hood for next-to-face comfort
Coated, water-resistant, lightweight main zipper provides superb wet-weather protection, and is deep for ventilating and is slightly offset at the chin in opposite direction of our Regulator® insulated tops for layering comfort
Single, glued-in, zippered internal, mesh chest pocket is high volume; pullover stuffs into pocket, with carabiner clip-in loop
Reflective heat transfer logo; enclosed elastic wrists
Radius cut bottom hem with drawcord; regular fit, sized to pull over underlayers
1.9-oz., 2.5-layer, 20 x 22 denier nylon with 40-denier ripstop yarns, a waterproof H2No® Storm HB (highly breathable) barrier and a Deluge® DWR (durable water repellent) finish.
184 g. (6.5 oz.)
The weight of this shell says it all: 6.5 ounces. The specter is an ultralight packer's dream. I can condense this entire jacket to fit in the front pocket of my fleece. Considering my storm shell usually stays at the bottom of my pack, I was looking to get something ultralight. I've used it in New England rainstorms, the Sierra, and during winter ice climbing and am very impressed with its breathability. The single zipper in the front provides adequate ventilation when needed, and the front pocket zipper sits high enough to allow access when wearing a hipbelt. The material, although lightweight, is very durable. The water repellent finish sheds water easily, and the hood has adquate room to allow wearing a helmet. Two small elastic chords allow cynching the hood around the face/helmet.
I actually have 2 different models of the Specter, both in medium. Although the beta says "Sized to fit over layers," I've found that one of my mediums is sized significantly tighter than the other. If you can get one, be sure to try it on and check the fit, and remember to think, "How many layers do I want to put underneath this? The tighter-fitting model that I have can still easily fit my fleece underneath, but I don't think either of them would allow a down parka. Personally, I don't wear my down jacket under my storm shell, so it's not a big deal for me. But I know some people put ALL layers under their storm shell, so it's something to consider.
On a final note, the dimensions of the jacket allow for good movement, especially when rock and ice climbing. The tapered fit at the bottom still provides lower-torso coverage while reaching overhead, and my movements seem unimpeded with the excellent fit of this shell.