Baseball Undershirt

What is the best undershirt to wear underneath your baseball uniform?

something like the pros wear or just something to keep mobility, but still is warm. something other than under armour, since it isn't warm enough
i do have the under armour longsleeve cold gear mock and it isn't warm enough in the weather as of now

You get a "liner" with colored sleeves.Matched to your colors.Cotton T material.

Clod's 20 Second Video 2