I wouldn't make a claim of "300 gsm" on the box like you have here. USPC doesn't use grams per square meter to measure its stock. It's a long story, but the end result is that they offer two stocks, period - a standard weight (Bicycle) and a heavier, casino weight (Bee Casino) which come in a range of thicknesses. The customer can only select the range, NOT the precise thickness. It's bizarre, but it's how they roll. Even worse is that the ranges overlap.
Bee Casino is the more expensive of the two and because USPC doesn't make the tuck boxes for that stock in-house, it adds something like eight weeks to the manufacturing time needed. Some people like to upgrade to Bee Casino because of the greater durability, some prefer using Bicycle because it's a fine stock, not as costly and can be obtained nearly two months sooner.