Pirelli Scorpion Pro All Terrain/Enduro Rear Tire Sizing

Hello all, i searched around to try to find the answer to this before i made a post and i am still unsure.. I just ordered a Pirelli Scorpion Pro All Terrain/Enduro Rear Tire - 120/90-18/ for some reason i thought i had 120/90 on before but after ordering i realized i had 110/90, the tire has already shipped and i am a little worried that it wont fit. I am trying to figure out if i should just send it back without mounting, saving me the trouble of mounting then unmounting. Any one have any suggestions? I'd really like to use this tire!


link to the tire


http://www.amazon.com/gp/product/B000KC163I




Thanks all!!

My old tires were actually 110/100, so these tires are just about the same size. I put them on and took my bike to the track to test them out and these things grip up awesome!! And they are DOT!