I recently replaced my worn-out set of silk long-johns with these. I've given them a good work-out commuting to work in the 28F - 40F temps we're experiencing right now in late December. The Thermo-Gear Premier is "cozier" and noticeably warmer than silk. In fact, I believe they'll be too warm to wear come Summer so I'll likely buy another set of silks so I'll be set year 'round. Nice touches on the Thermo-Gear Premier includes the thumb holes on the shirt sleeve cuffs, which makes layering up a little easier, and the dropped back on the shirt. These make an excellent base layer for colder temps and I'm sure I'll get many miles out of them. Highly recommended!