The Maestrini brass flanged 3/8" BSP female lock nut has a diameter of 36mm (1/4") and is rated to 580 psi. Please be aware that if used for through hull applications, the locking nut fitting must be correctly electrically bonded in order to prevent corrosion. Brass is not recommended for below the waterline, due to it being susceptible to dezincification. Sold singularly.