Rear sprocket

[BigOkie]

So I'm putting my new chain and sprockets on today and the rear sprocket has beveled holes in between the mounting holes like this one,
http://www.amazon.com/dp/B00918SG3U...e=df0&creative=395109&creativeASIN=B00918SG3U
What are they for? Should the bevel face in or out if they are for some kind of accessory?

 

[BigOkie]

Must be to multi purpose it, but it does make it lighter. Anyway it's on now.