The needles are size 7, as shown on the ends of the metal ones, or 4.5mm if that's the measurement you're used to. The plastic is yes, from single use bags, and knitting yesterday I went through the white and red ball which was so much thicker than the rest that I now have about an inch that is wider than the rest of the knitting, lol. But I'm not picky, that's OK. 😂 I had chosen that bag for having the same texture as the others - the stretchier kind of plastic rather than the more brittle kind, if that makes sense. I had actually gotten all these bags from my parents' stash, because I don't generally get plastic bags on my own. The blue and orange are from newspaper delivery!
Ooh you may have some better ideas than what I was thinking to make, I may have to change tack... ;)
!BEER