XS Scuba Hookah RegulatorThe term hookah refers to the breathing gas being supplied from the surface. Features: RG303 uses an intermediate pressure of 5080 psi (3. 55. 5 bar) Often used with compact specialty compressors RG305 uses an intermediate pressure of 80110 psi (5. 57. 5 bar)Often used with larger, commercial grade, specialty compressors RG310 uses an intermediate pressure of 110140 psi (7. 59. 5) bar Typically used with scuba cylinders left on the surface with a long