Rajsun Cotton Stretchable T-Shirts

A T-shirt or tee shirt is a kind of shirt which has short sleeves. These sleeves cover the shoulders and the top of the arm, but they do not cover the elbow or the forearm.
A round neck T-shirt is the most common style of neck. As the name says, the neck opening closely fitted to the contour of the neck.
The T-shirt in the image appears to be a crew neck style with short sleeves.
The fabric seems lightweight, possibly cotton or a cotton blend, given its casual appearance and the common use of cotton in T-shirts