Sienna Miller's Twenty8Twelve, what stars really wear off-duty...and it's attainable.

By Laura Medina

What do celebrities actually wear when they are not posing in haute couture at film premieres or upscale film festivals or award shows?

Fellow actress/celebrity, and jet-setter, Sienna Miller, knows what her fellow celebrities want.

Her Twenty8Twelve clothing line reflects a chic, fast-foward and fashion-forward sensibility that adapts easily to any locale and climate. Not extremely warm. Not extremely prim. Not extremely cloaked for the freezing cold. It is just right transitional layering great for tossing on while on the go.

Recently, Taylor Swift was hanging out with a friend in Central Park, in a Twenty8Twelve Daisy Dress that can be had at $295 on www.shopbop.com.

Back in May, Naomi Watts was tooling around town, in Manhattan, with Liev Schreiber in a Twenty8Twelve Spring 2011 Laurie T-Shirt. Www.revolveclothing.com sells this for $135.

What is truly cool about Sienna's Twenty8Twelve line is how effortlessly and how seasonlessly it is. It perfectly plugs in the gap between too summery sultry and too winter chilly. Just right.

Her line makes some great and cute crop leather jackets.

Zoe Kravitz rocks her crop leather motorcycle Bohemica Jacket at "X-Men: First Call" London premiere, over a simple white tee and black mini circle skirt.

Sienna pulled herself together in her own aviator-influenced, tanned brown, leather Spring 2011 Dok Vest with wool shearling, over basic lycra black tank and leggings. Www.zappos.com has it at $699.

Twenty8Twelve also does sleek basics that can anchor accessories and shawls and wraps.

Here, Sienna models her Autumn/Winter Titon Dress in Black that retails for $448.

Now, you can rock it like a celebrity, thanks to Sienna.