I had the Mojo's....
Peeps are made to work when they are close enough to 'look through and not see' them.
The others...
I don't recall the exact details, but There's some issue with the way they are held on, and that being the takedown pin to disasemble the rifle for cleaning...
I LIKE Peeps on AR's, FAL's, and ESPECIALLY M1A's and M1's etc....
Not worth it on the SKS due to the above...
Funny, Everybody 'complains' (See mods, I'm working on it) about the sites on the SKS/AK
But never the 30-30 or Mauser....