OK
I am sure this is posted elsewhere but I could never get a part number and a location to buy 520 sprockets from.
So this is what I did.
I called Sidewinder Sprockets and manged to get sprockets ordered.
They ended up arriving loosley packed in a padded envelope.
Steel front sprocket had not been ground to size (thinned down to a 520) so I had to send it back. Part number was 1180 - 18 t. I paid $69.99.
"Billet" aluminium rear sprocket was hard anodized silver (a most disturbing colour) and was just a standard rear sprocket not the fancy sprockets that side winder are known for. I paid $109.00 for it.
So I packed up the front sprocket to send it back and at that point went mental and decided that I didn't want to wait for another company to fix their F'up so I ordered them again from Drive Systems USA.
www.drivesystemsusa.com. I decided that I would call them and I ended up ordering part numbers...
Front Sprocket 88801-18 paid $ 38.95
Rear sprocket 87602 H43 paid $ 69.95 and the bloody thing is hard anodized black.
Both were AFAM parts
Both were in stock and I ordered them Thursday afternoon and they arrived today and are already fitted..
So screw Vortex who have the most misleading website and the least helpfull customer service. (Sent me the first wrong sprocket).
And I am done with Sidewinder another $200 F-up I made and the second wrong sprocket.
But a big thankyou to Drive Systems USA.