Specifically designed for those who sleep on their sides, the patent-pending Sidewinder Series was engineered to ensure warmth, comfort, and ease of use no matter which side you're on. Constructed with features you expect from a traditional mummy bag with additional body-mapped insulation to optimize warmth where you need it and minimize pressure points and other 'side effects'. The Sidewinder SL is a side sleeper's dream bag with technical features that roll seamlessly from one adventure to the next, and from one side to the other at night. Women's specific bags differ in shape and fill weight with a less drastic taper from shoulders, to hips, to feet - reducing cold spots and creating more warmth where it counts.