It's a joke shirt, about fire hydrants. Some people call them plugs... but they also call their dealer a plug, so you're supporting your local plug... it's funny. Buy the shirt. 

50% Polyester 25% Combed and ring-spun Cotton 25% Rayon
Extra Light fabric (3.8 oz/yd² (110 g/m²))
Sewn in label
Retail Fit