I'm 6'3 with a lean muscular build. I used to always buy standard XL tshirts and I wear tshirts under my work clothes daily. After a few washes the standard length shirt would always be too short and couldn't stay tucked. Also, with the XL size the sleeves would sometimes pop out below the sleave of a leaner fitting polo. The large/tall size solves both of these problems. It fits really well, is very soft, and the collars stay perfect. That's all I'll buy from now on!