Abstract: Regulators and/or parts or components thereof useful, for example, in systems for powering pneumatic tools. In certain embodiments, dual-stage regulators wherein each stage of the regulators is adjustable and/or tunable. In certain preferred embodiments, tunable and/or adjustable dual-stage regulators which are capable of being used, selectively as desired, in low and/or high pressure applications, shot-type and/or continuous flow delivery applications, and/or low and/or high volume applications (or any combination thereof). In certain additional embodiments, in combination with or separate from the features of other embodiments described herein, regulators which exhibit stable performance regardless of, for example, cylinder supply pressure.