Silicone hose 23.5 x 4mm. (per meter)
Inside size: 23.5mm
material thickness: 4mm
Outside diameter: 23.5+ (2 * 4) = 31.5mm
The big advantage over the other hoses is that these silicone hoses remain flexible even after years, and sound dampening works, the resonance that pumps can produce are absorbed by the hose.