I'm 5ft 9in and about 170lbs. In a tailored suit or jacket, I would be 40R. This puts me right on the borderline between M and L when it comes to t-shirt sizes. Some of the larger sizes may be too big for me, but this one fits perfectly. A medium size would be too small. These shirts are also of good quality.
AM Fitted T Shirt 3 Pack for Men's Clothing - T-Shirts & Tanks
46 Review
Ashers Apparel Schrute Breakfast T Shirt Men's Clothing for T-Shirts & Tanks
34 Review
Ultimate Comfort and Style: Minus33 Merino Wool Ticonderoga Lightweight Men's Clothing, T-Shirts & Tanks
43 Review
Men's XXL Super T Mockneck π from Lands End - Clothing, T-Shirts & Tanks
32 Review
Men'S Long Sleeve Polo Shirt - Slim Fit, Stretchy, Breathable Collar
43 Review
H2H Mens Casual Slim Fit Short Sleeve T-Shirts Cotton Blended Soft Lightweight V-Neck/Crew-Neck
46 Review
Van Heusen Traveler Stretch Men's Shirt
47 Review
Men'S Regular Fit Short-Sleeve Dress Shirts By Allsense - Look Stylish And Professional!
41 Review