A great base layer is an essential part of any complete cycling wardrobe. You can wear super light summer jerseys in spring and fall weather. If it's winter and the air is cool, then layering with quick-drying fabrics helps you stay dry while you climb so that you can descend without sweaty chills.
I've always loved having a few great base layers, and use them throughout the year on all but the warmest summer days. Personally, I also have almost always worn base layers during crits just in case I take a fall, in order to provide another layer of fabric between my skin and the ground.
This base layer is pretty premium. It's got a stretchy, tight fit and is made of very lightweight wicking fabrics. The main fabric is Italian 110 gsm lighweight mesh with an antimicrobial coating to reduce odor. It's UPF 30 protective against bright sunlight, so for those with sensitive skin, you can wear this under your jersey to stay dry and avoid sunburn.
And, unlike many base layers that are all white or all black, this one has some bright colors to lighten your mood while you get kitted up before your next ride!
* This base layer comes in Euro sizing... Nate here is 6'2"/188cm and 165 lbs/75kg. He is wearing a medium base layer, medium bibs, and wears a small jersey over the base layer.