This is an officially licensed Its Always Sunny In Philadelphia product.
This t-shirt says "Paddy's Irish Pub" inside a shamrock and says "Worst Bar in Philadelphia Where You Can Drink at 8 in the Morning"
Sheer t-shirts are made of a soft material and are slimmer fitting than your average t-shirt. Sheer t-shirts are generally made of a cotton/polyester blend, but may also be 100% cotton. The shirts are not see-through nor is there any loss of quality.