18/1 100% Authentic 100% Officially Licensed Classic Fit, Heavy Weight Tee-Gildan Color: Black 30/1 and 18/1 refer to the gauge of the garment thread and the number of stitches per inch. An 18/1 T-shirt is a standard T-shirt. A 30/1 garment is constructed from finer thread with more stitches per inch. This results in a softer and thinner garment with a more fitted cut than the 18/1.