Help wiring tankless water heater.

[Rozmere]

Okay, so a while back my old water heater tank for my mobile home finally gave up. It isn't as easy as replacing an element this time, it's totally dead. So I need to install a new tankless water heater and I'm planning on getting the "Ecosmart Eco 18". The plumbing part is a no-brainer, I've done tons of plumbing but I've only done a little electrical work and it's been years ago so I need advice. BTW I have very little money so that's why I'm having to do this myself.

The specs for this water heater say kw: 18; volts: 240; breaker: (2) 40 A; required wire: (2) 8 AWG

So I want to make sure I get the correct wire and breakers. So are these items what I need? Do you have different suggestions? (BTW the water heater will be less than 25' from the breaker box that is in another room)

(2) Wire: https://www.amazon.com/InstallGear-...lja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

(2) Breakers: SIEMENS Q240 40-Amp Double Pole Type QP Circuit Breaker black - - Amazon.com - https://www.amazon.com/Q240-40-Amp-Double-Circuit-Breaker/dp/B00002N5HK/ref=sr_1_5?dchild=1&keywords=40a+breaker&qid=1622406422&sr=8-5

(1) Ground Wire: Copper Ground Wire MTW 8 Gauge AWG Green/Yellow Stripe 19 Strands 25' FT: Amazon.com: Industrial & Scientific - https://www.amazon.com/gp/product/B07PRXCTBP/ref=ewc_pr_img_1?smid=AF5R0QSE27JYB&psc=1