With many different Fret Shields, make sure you choose the one that fits your fret scale size by using a tape measure or ruler, align the 1" mark with the inside edge of the nut and measure to the center of the 12th fret. Take the difference between the measurement and 1" and double it to calculate your guitar scale. Use the Music Nomad Tri-Beam Fret Scale Ruler MN820 (sold separately) to determine your fret scale size and which Fret Shield to buy. Common 24.75" fret scales are mostly Epiphone and Guild electric guitars.