Snow chains – Question about size

Hello! I wanted to buy snow chains for my matures of size 155/70/R13. at atu they are too expensive for me and I was now in the construction market. there hangs a list and with the mature size I would need the size 3. now they have but only size 4 as the smallest hang there. at size 4 it also stands among other things: 155-13 (but without specifying the ripe height). as I understood, you can also tension the chains. can I take the now for my mature size or not? atu they told me that the 100% have to fit. but if you can span, then I can get the size 4 really tensed maybe also on an unstressed size 3?! write with all the inspirations you have! already thank you! mfG Sebastian