They seem a bit small, at least to me. I'm 5'9" and 180 lbs. I always buy plus sizes shirts and all but these have plenty of room. Flannel. If you want to wear it under another shirt it will probably fit you. If you have a looser one If you like the shirt you can take one size up The material seems to be of decent quality.
Carhartt Workwear XXXXX-Large Men's T-Shirt β Original Clothing for T-Shirts & Tanks
34 Review
Men's XXL Super T Mockneck π from Lands End - Clothing, T-Shirts & Tanks
32 Review
Next Level Premium Fitted N6210: High-Quality Men's Clothing & Essential T-Shirts + Tanks Collection
39 Review
Hanes Sleeve T Shirt Large White Men's Clothing T-Shirts & Tanks: Premium Comfort and Versatile Style
33 Review