You will find that Gildan makes a great base for layering under flannels or jackets.
Gildan G640 Adult Softstyle T-Shirt Ringspun Cotton Crew Neck Plain T-Shirt
A crew neck design keeps the collar area clean and free of extra fabric.
Hanes Men’s White Crewneck T-Shirt 6-Pack Undershirt Tee TAGLESS FreshIQ Comfort
A nice touch is how Hanes pre-shrinks the fabric so your size stays the same.
Men’s 100% Cotton Tank Top A-Shirt Wife Beater Ribbed Undershirts Size: S-4XL
I like that the round neck is neither too high nor too low on the chest.
New 3-12 Pack Men’s 100% Cotton Tagless T-Shirt Undershirt Tee Plain White S-XL
You will notice the solid pattern helps the shirt drape nicely on the body.