Bolter T-shirts - a great basic men's t-shirt - this 4 pack of tee shirts from Bolter is just what the wardrobe ordered. This is Bolter's super soft lightweight everyday crewneck tshirt. Use it as an undershirt or wear it as an outer shirt on hotter days. The plain or solid color shirts are 100% cotton - nice and cool for summer time or for layering. The Heather colors (heather grey, heather charcoal, heather brown, etc.) are a cotton/polyester blend. 60% Cotton 40% Polyester. The heather grey color pack is 80% Cotton + 20% Polyester. The 100% cotton colors will shrink a little in the wash (about 5-8%). Keep in mind these have a european cut to them so they are slim through the body. If you're in between sizes we recommend sizing up. The cotton/poly heathers will not shrink as much and is something to note (3-5% shrinkage). Sizing Details (Chest Measurement) Around the Body: Small: 33-35"Medium: 35-38"Large: 38-42"X-Large: 42-46"XX-Large: 46-49"3XL: 50-54"4XL: 53-58" Which Fabric Fits You Best? Cotton/Polyester = "Heathers" or 100% Cotton. Both with Soft Hand Feel. Cotton is Cooler - while Cotton/Poly Washes & Dries Nicer