This is a set of two black, long-sleeved undershirts. Both were worn for about 10 games in amateur baseball, but I am selling them now as I have retired from playing. - Brand: Under Armour I don't think these are specifically for baseball, but they don't have excessive tightness and have a zip-up chest, so I wore them for warm-ups. Also, while they are HEATGEAR, they have a mesh design from the back to the sides, making them highly breathable. - Brand: ZETT These are compression fit. They are generally for spring and autumn, but because they are relatively thin, I also wore them in the summer for sun protection. Thank you for looking.