The size varies greatly, from 13 cm thin cavity pocket portable model, to 35 cm thick cavity, a variety of styles. According to the basic principle of the instrument, the larger the cavity of the worry-free drum, the better the resonance, the more thick and ethereal the sound, the longer the sound. And the cavity of the small worry-free drum, the resonance will be relatively poor, the delay will be relatively short, and the timbre will be thinner and clearer.