MLB Seattle Mariners Batting Practice Jersey 100% polyester Imported Features authentic full front or left chest official logo & Authentic Collection jock tag. Cool Base Technology, along with ventilated stretch mesh armholes and side inserts provides moisture wicking & comfort. Single placket design with a Cool Base, 100% polyester mock mesh body. Officially Licensed by Major League Baseball. Available in Official team colors & logos. 165 Gsm, 100% polyester mock mesh.