frame diameter help?

[a1steaksauce]

I have an xs400 81 SOHC and was wondering which bolt on peg diameter I should buy. The original passenger peg mounts have been chopped off, but the frame is still an xs400 frame.

i have the option of choosing 1",1 1/8", and 1 1/4".
I'm not exactly sure, but I think it should be 1"?

 

[a1steaksauce]

in case anyone else was wondering, it seems that the frame is 7/8" throughout and the part that goes to the rear wheel is 1-1/4"