Plastic washer size question

[Faerie-StarV]

I really apologize for being the dumbest person alive who has still trouble with the measurements but I need some help, it's about the plastic washer sizes. 
I want to order them so I can get started for my custom ponies but I don't know what size I need for the G1 ponies and I always get mixed up with cm, mm, etc.(I only know inches and foot but the rest? Forget it as I always struggle with that when I was a kid). I was able to find this on Amazon but the measurements stumped me. https://www.amazon.com/uxcell-Nylon-Washers-Screw-Thick/dp/B07NRWY1H8/ref=sr_1_1?dchild=1&keywords=clear%2Bplastic%2Bwasher&qid=1586384044&s=industrial&sr=1-1&th=1

I want to order them but I can't tell the sizes very well so if any of you can tell me what you usually get for G1 ponies, it would be really great. I already added the re-hair tool to my cart as I don't have it and planning to order other nylon hair soon.

[tailrustedtealeaf]

I've been using zip-ties, but I think this would be a good size for use in ponies.

[Griffin]

I think these are too small for adult G1. The original washers appear to have a 6 mm hole, so twice as big as these (btw if you check the images, there's one which has the measurements in inches!) Can you find any plastic ones in size M6? Many people also like to make the tails on their customs a little thicker. I've occasionally tried to use washers harvested from ponies but I usually struggle pulling the tail through them... 

Zip ties are always an option, or you could even use string. I usually add a dab of glue as well, just to make sure no hairs are pulled when combing the tail, but this is totally optional.