What injectors?

Hi, I am hoping someone on here may be able to help me. I have a 1983 mk1 GTI tintop with a kjet system. Recently it's been not idiling very well and I have noticed the lines going into the wur has correded. So I am looking at new injector lines from HEL only it says for M10 injectors and I'm a little unsure what that means. I have also seen the lines on VW heritage but again they say they are for M12. I know that's for bolt measurements but was hoping I could get the lines without taking a bolt off to check. Does anyone know what bolt size lines I would need? Thanks in advance