As the title suggests this mandolin saddle is for radiused (not flat) fret boards. The string grooves will be cut lightly in the top of the saddle. See below for string spacing specs. These saddles will fit most mandolin bridges found on production mandolins with little or no modification.
What does radius mean? The radius refers to the shape of the fret board. Most are flat. Some fret boards are curved from edge to edge (side to side or another way to say it, from G to E). A 12″ radius is the “standard” and equals a curve that would match a 24″ diameter circle.
What is the hole spacing? The distance between the center points of the “post” holes on my saddles is exactly 2.285 inches. Refer to the diagram on Stewart McDonalds website for more detailed measurements by clicking here: StewMac
What are the “post” hole diameters? The holes in my saddle are drilled with a 9/64 inch drill. This equates to .140 inches. I can enlarge the holes if necessary. Put that in the comments space during ordering.
What is the string groove spacing? From the center of the outside G string to the center of the outside E string is approximately 1.625 inches which is equal to 1 5/8 inches.
Will the antler saddle fit my bridge? My saddles fit the bridges sold by Steward McDonald (see link above in the “Hole Spacing” question). If your bridge measures the same or within a few thousandths, then it should fit.