Are AR-15 Rear Sights Interchangeable?

I always wondered about it, now I know. Thanks.
But to tell you the truth, I still like the old styled M-16 carry handle rear sight better, maybe because I'm old school. Picture was taken in Sept of 1975.

TSgt Joe C. PO3 Steven Sherrill CW3 Kevin Storm SSG (Join to see) SGM Steve Wettstein SMSgt Thor Merich MSG (Join to see) PO1 John Johnson MAJ Ken Landgren LTC Greg Henning PVT Mark Zehner MSG Tom Earley Alan K. SPC Mark Huddleston PO1 H Gene Lawrence SGT Elizabeth Scheck Sgt Deborah Cornatzer SSgt Boyd Herrst SPC Diana D. SPC Nancy Greene

Hey, I flew airplanes so have no idea! :-)