Get 2, save $10, and don't run out!  Thirsty, older woods take more per gallon (120-180 sq ft per gal is common on old wood, 200+ per gal on new).  Do you have 400 sq ft of newer wood?  If so you are going to need 2 gallons!  Product stores for years if never opened or tightly closed.  Ships 2 to a box and saves cost so you get the savings!  Thanks!