The 1301/1901 are both Classic styles. Please see the model #'s on this page here:
https://www.tshirtgang.com/cp/pricing/matrix
There is a mix of the models from AlStyle to fill some of the sizing and color requirements. One style from AlStyle doesn't cover all the colors and sizes, so there is a mix to fill the gaps. 1301 will be used for 4/5/6XL