I just went from 29mm to 19mm due to the fact Iam sighting in 20-30-40-50-60 yrds and the 29's were to big past 40 for me(its a eye thing or age)....and the 10's might be too small for me.....All my other sites were set at 20-30-40 and thats it,been like that for 24yrs.....Now on my 25th year needed to change afew things...