Heating Element - Questions on SSR and Voltage

[Brokenjeep]

Hey everyone, I picked up a 50l milk can the other day and had a few parts for an electric element thrown in with it!

He threw in:
2 x SSR – Fotek SSR-25 VA 25A/250V
1 x Element - Camco 02613 6000W 240V Screw in Water Heater Element Foldback
1x RV4NAYSD504A - Rotary Potentiometer

I found Still Dragons econobox build instructions with 1 SSR and will have no problems following the schematics to wire it as demonstrated but I have some questions.

I had intended on running it on 20A 120V but since the Fotek and Element are listed at 220v will I need 220 or will it just under perform on 120?

I should also add that I have a healthy fear of electricity and have done lots of work and had it inspected by ESA before, just haven’t worked with elements and SSR’s.

I searched the forums but sadly didn't see any questions/answers so basic... and this is my second post here so hopefully I didn't break any rules. Thanks in advance!