When I have used this site in the past I have typically ordered the front site closest to what came from the factory and the next blade higher. Over the years this has worked pretty well.
here is what NECG says
"Because original Ruger factory sight beads are supplied in various heights you will need to measure your original bead to determine which size of replacement bead you need to order. To do this you will need to remove your original bead. Simply press down on the locking plunger while tapping the sight toward the muzzle with a plastic punch or piece of hardwood. Once your bead is removed, measure it from the bottom of the dovetail base to the top of the bead. Should you desire to change the point of impact of your rifle we suggest the following: to RAISE the point of impact, order one size lower than your original, to LOWER the point of impact, order one size higher. Please note that our Sourdough Sight Bead is available in only one height, .433", but because of its design it can be filed lower to raise your point of impact. The NECG Beads for Ruger Rifles are manufactured to match original Ruger beads as closely as possible. Should the base of your new replacement bead be too large for your rifle's dovetail slot, simply file or lightly sand the bottom of the bead's dovetail base until it will fit.
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Hope this helps, they are a great site. Let me know how you make out.
I will more than likely be trying the same thing when I get mine.
Dave
