There are a whole family of clarinets of various sizes.
The smallest is the Ab clarinet. It’s so small, in fact, that many players cannot even play it because their fingers are bigger than the keys and the tone holes.
The Eb clarinet is about half the size of a Bb clarinet and is used for color in both band and orchestra.
What is the difference between the B flat and A clarinets? The Bb clarinet is the main clarinet, used in both bands and orchestras. The A clarinet is a slightly longer clarinet with a darker tone and half-step deeper pitch, used almost exclusively as an orchestral and solo instrument.
After that, there are the alto, contra-alto, bass, and contrabass clarinets. There is also a very rare sub-contrabass clarinet that plays an octave lower than the contrabass.