I have probably owned about 10 of these over the years in both 1 1/4 and 2 inch and found them all to be very good optically and mechanically .
When I lived in Darwin a few of us got together and did a blind test with an AP , TV and a Bintel 99% diagonals using TV Radian eyepieces and a well cooled and columated Takahashi M210 and Takahashi SKY90 to tell the truth there was nothing any of us could pick between these 3 , yea these GSO ( Skywatcher ) diagonals are very good for the price .
Brian.