Flex watt install

What type of cord should I use to run my flex watt? I'm doing a 5 high rack and wana run it in parallel. Is it just 14awg lamp cord(thhn)? Or something else?

i've always used a #16 wire on my racks and it works great, so i think a #14 would handle it a lil better. i've used it to wire 6inch heat tape parallel and long strips snaked through racks 5-8 levels high.