Russian guitar usually differs from the wood in the rest of the neck. The neck joint or heel is the point at which the neck is attached to the body of the guitar. The fingerboard is made of hardwood (ebony or rosewood are common), fitted with metal frets of brass or steel. Fret spacing almost always follows the western twelve tone equal temperament (12-tet) system. The surface of the fingerboard may be flat or curved slightly ("radiused"), although the curve on the Russian guitar is usually somewhat less than that of an equivalent western 6-string guitar. Inlayed position markers are common, and
Ten-string guitar has a single neck and allows all strings to be fretted. While the six-string classical guitar remains the standard and most common instrument, since 1963 ten-string guitars in similar configuration to the original Ramírez have been adopted by many classical guitarists and produced by several first-class luthiers, using both Yepes' original tuning and others. The Halo Guitars XSI is a solid body ten-string guitar with ten individual steel strings, two EMG ten-string pickups, and a Kahler ten-string tremolo bridge. XSI is an acronym for Extended Scale Instrument. Halo Guitars tunes the XSI from low to high as follows: A+D+G+C+F-B♭-E♭-A♭-C-F. Agile