I ordered mine online, so I didn't have the opportunity to go through multiple pairs looking for a good "fit." Fortunately they fit just fine!
I had trouble putting them on my doll's face at first. I'm not sure what I was doing, because after 20 minutes or so I "got it" and they've been kind of a snap ever since. I think it is a matter of gently working the "arms" into her hair for stability.
I'm an adult collector and haven't had a quality problem. I'm not sure how they would hold up to active play, but for display purposes I'm quite pleased!