The metal frames can be adjusted slightly for tighter or looser fit. Simple technique.
To make larger:
Hold frame by hinges with lenses face chest. Slow pull frames on ends of the hinge and slightly bend frame in the middle but no more than 1 inch in flexing. Do this 5 or 6 times with slight force and then try on. If still to tight, repeat step one over until you accomplish the desired fit.
To make smaller:
Place fingers on the exterior of hinges or use palms to press inward. Press inward 5 or 6 times and try on to fit. If still not small enough repeat process.
View Speed Demon & Pioneer Owners Manual