What is "bass flute"

The bass flute is the bass member of the flute family. It is in the key of C, pitched one octave below the concert flute. Because of the length of its tube (approximately 146 cm), it is usually made with a "J" shaped head joint, which brings the embouchure hole within reach of the player. It is usually only used in flute choirs, as it is easily drowned out by other instruments of comparable register, such as the clarinet.