Buying clothes online is usually very tedious, the fit cannot be checked and returns can be annoying. First, clothing must be sold in US size. I have the XXL and it fits like a large, they should be snug on the chest and arms, flow in the middle and be a bit longer than regular t-shirts.
Ashers Apparel Schrute Breakfast T Shirt Men's Clothing for T-Shirts & Tanks
34 Review
Next Level Premium Fitted N6210: High-Quality Men's Clothing & Essential T-Shirts + Tanks Collection
39 Review
Carhartt Workwear XXXXX-Large Men's T-Shirt β Original Clothing for T-Shirts & Tanks
34 Review
Hanes Sleeve T Shirt Large White Men's Clothing T-Shirts & Tanks: Premium Comfort and Versatile Style
33 Review