I've always had to use the 5 sheet customs. 1 is my copy. I mail care packages. Wouldn't be allowed to do it without the 4 piece. The copies fit nicely in the clear sticky-backed envelope made just for them.
You can order all supplies online and have them delivered to your home. I also do home pickup with the packages hidden in a planter box. I fill out the customs forms by hand as I had several problems with the online form a few years back.