Do like I did.
I bought PIAA wipers also, just take 1 of the middle sized adaptors and slide it on the wiper arm. I know its not the largest nor smallest ones.
I believe out of the remaining two adaptors, one will fit the curve of the wiper arm, think the other is too narrow for the arm curve. Just take a screw driver and remove the clip and place the wiper into adaptor.Pretty sure out of all the adaptors one will fit the wiper arm.
Sorry I threw the instructions out, but dont put the wiper on adaptor till you found correct one. Its alot easier this way.
Hope I could help.
Dembones