Williams FireSights, and possibly the TruGlo & HiViz fiber optic front sight blades also, are ALL available in a wide variety if heights, two colors (red/green) and two bead sizes (1/16"/fine & 3/32"/coarse).
First, check the sight height calculator on
www.skinnersights.com to calculate the exact height you will need.
IMHO, it's better to buy a front sight slightly higher than indicated.
Second, go the the Williams Gun Sight Co website (google), and see the sights (
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)
Midway has the sights, in all the heights and base widths.
FYI -
The "N" narrow base sights are for specialty/narrow ramps like the Williams Shorty and some rimfire rifle's;
the "W" wide base sights are for mounting directly in a barrel dovetail (no ramp);
the "M" medium width base sights will fit most other ramp-mounted applications.
.