This is the first and only Tremolo harmonica we carry that is available in all 12 keys. Tremolo harmonicas are Diatonic models constructed with double holes, each containing two reeds tuned to the same note, one tuned slightly higher than the other. Since both reeds are either blow or draw, when played both will sound together - the slight difference in tuning creating a beautiful vibrating or tremolo effect. Tremolo models are popular for ballads and gospel music, as well as for Latin, Asian, European and other international folk styles. 24 double holes, 48 reeds, airtight plastic comb, 7 inches long by 1 inch wide. Comes in its own zippered padded nylon canvas case with carrying strap.