Electric mandolin and "EM-8", with carved top bodies and four and eight strings respectively. Blue Star produces four and five string models under the name "Mandoblaster". Jbovier produces four and five string "EMC" electric mandolins, which resemble the Fender electric mandolins, and a four string "ELS" electric mandolin. EMC stands for Electric Mandocaster and ELS stands for Electric Leo Smith. The Eastwood Guitars manufactures solid body eight string electric mandolin under the name "Mandocaster". It has Telecaster resembling body, two single coil pickups and a pickup switch known from Stratocaster guitars. They also make "Mandocaster 12" which is actually an octave guitar.
Mandolin suit them to Cai luong opera music. In the mid-1930s, they made concave frets, scooping out extra wood between the frets, making the space between them deep and to allow the musicians to bend the notes, and stringing them with four single strings. Musicians Hai Nén and Hai Nhành were associated with the instruments, possibly being the first to use them. The "sunken-fret mandolin" (mandolin phím lõm) did not meet the musical needs as well as the sunken-fret guitar, because the mandolin's rigidity made it painful to get the same effects from the strings. Also the mandolin's narrow fretboard made