We use these t-shirts under long sleeve t-shirts for extra warmth. The composition is 100% cotton, but does not shrink badly. They are a good size (although we like to go up a size to add length. Note: I buy them when the price is under $3 (sometimes under $2) - at that price they are ok. Note also that they can be worn as a t-shirt, they are quite simple and with us almost always a t-shirt.
Boys' Long-Sleeve Disney Star Wars Marvel T-Shirts by Spotted Zebra
46 Review
Soft Brushed Fleece Crewneck Sweatshirt for π Boys and Girls 4-12 Years - Kid Nation Kids
42 Review
The Good Day Lab Clean Shield: Ultimate Comfort and Breathability in Tagless 4-Way Stretch Polo
43 Review
Star Wars, Marvel, and Disney Short-Sleeve T-Shirts for Boys from Amazon Essentials
50 Review
π Fruit of the Loom 6 Pair Cushion Ankle Boys' Clothing: Comfy and Stylish Selection for Active Boys
57 Review
π₯ Stay Warm and Active with Rocky Fleece Thermal Underwear Bottoms for Boys
44 Review
Funny Guy Mugs Tearaway Sweatpants: Playful Boys' Clothing for Fun and Active Days
49 Review
Arctix Youth Pants Reinforced: Large Boys' Clothing for Active Adventures
46 Review