Zack Brown Glass 20mm Stopper (2nd Quality)

Perfect seal as always from Z.B. His Q.C. is impeccable, I can't find any reason whatsoever as to why this is a 2nd. Used a few times but find I mostly use my marbles or matching caps. Tight fit design makes it very difficult to fall off. This Cap is a 2nd Quality!!! Some minor visual imperfections that I cannot identify but function and seal are 100. Been used a few times and cleaned with Iso after use. Thanks for looking! ***2nd Quality