Search:

They are made from plastic that is quite soft, and then is easily cut.
They are 8cm long so i make 4 pieces of 2cm for each of my tarp guylines, more than enough to me.
...

Thanks for the comments.
I use 2mm guylines and they fit perfectly, i can slide them up and down easily.

Plus, they are quite inexpensive, about 5€ for 36 pieces, and i think i will cut them to...

Last week i found some spoke reflectors in a shop.
Though it would be a good thing to add to my tarp guylines, and in fact, it is :)

Weight nothing, and effective.
...