Low pressure or high pressure? Material? Starting from a tube or billet? Tie rod, threaded end or screw in endcaps? Standard size of full custom?

Also, selling rams is an expensive proposition. According the rules every custom piece needs an independent certification.

9.7 Rating
All pneumatic components used with pressures greater than 50psi (3.4bar) must be rated or tested to at
least the maximum pressure available in that part of the system. You may be required to provide
documentation or certification to support this.
9.7.1 Custom Components
Custom made components, or parts operating above the suppliers maximum working pressure, must be
independently tested and certified at 120% of the maximum system pressure available at that point.