The Bosch "Direct Connect" and "Micro Edge" fit properly on the stock SWF arms (if a little snug as Mark mentioned). Not sure about the funky all plastic ones.
If you have one of the two types I mentioned, you might double check the fit and also see if some PO "tweaked" the arms to fit a wrong blade.
BTW, wiper blades are one of those items where the typical retail store markup is like 400%. I try to remember to order them when I need something else (to get free shipping).
Bosch Micro Edge
GPR
$5.87
AZautohaus $5.66
Autozone in Dallas $10.19 Ouch