Is your 10/22 a very old or very new model? Is it new, or used? If used, did it still have the original sight in the rear dovetail, or a replacement sight (could be a sign that the previous owner had already filed-off some metal in the dovetail to get a new sight to fit)?
Apparently, some other folks have
had problems with this sight set. Here are a few reviews from MidwayUSA's website page for this product:
from Fargo, ND
"These sights are o.k. but there were a few things I don't like:1.) The rear sight was too loose in the dovetail. I could slide it right through by hand with very little resistance. I had to use shims and loctite 680 to get it installed correctly. My factory sight is snug so I'm not sure why it didn't fit."
from North Little Rock, AR
"Front sight fit fine. Rear sight fell right off. HIVZ is sending me shims."