Good adjustable full flow regulators like watts with a gauge are not cheap, but are worth it.
This new one may be an exception for those who don't need adjustable or with a gauge.
NEW PRODUCT!! Fairview 55 psi inline regulator with great flow. This is what everybody has been waiting years for. Expect little difference from what the spigot can put out. Not adjustable or repairable like the Watts units, but very economical with high performance for those not willing to go with the more expensive units.$24.95