Product review (5 stars): Excellent quality
Don't waste your $ on cheap plastic covers.  I bought these at Menards for $9.99 -- not sure why so much higher at other places.  Anyway, heavy gauge steel, epoxy painted, dampered cover (no noise!), and spring tension (no flapping in the wind).  Screen to keep out critters.  These will last forever, unlike the plastic ones that rot-out, are noisy, and birds get through.