I have never used these before - mind you, it's nearly 12 years since my last litter! But I am considering buying some as I have some very similarly marked puppies. They are only a couple of days old at the moment. I do have some paper type ones but they won't last very long!
But I do have concerns about puppies getting caught up in each other's collars. Am I being foolish or can you get collars that break in the even of this happening?
Any advice gratefully received.

I actually found the paper ones to be dangerous. They don't rip at all and if you get them on too tightly, or the pups grow quicker than you expect, they cannot be adjusted. I used them for about 3 days then had to cut them off with scissors which was quite scary. Then bought velcro ones. Used newborn size for a fortnight then swapped to a bigger size. Was easy to check sizing every day and adjust quickly but they stayed on until pups were 8 weeks when they started to take them off each other as they got so strong. Had no problems with them at all.

Used the ones with small clips and adjustable as pups grow.No problems at all with them and inexpensive.

Used the paper ones once and would not use them again. Mine are marked with tippex in a certain spot from birth and has been a system that works for me. There are always specks left and I just retouch regular.

WhelpIDcollars!  I always have puppies who look exactly the same and have used several different types over the years.  These are brilliant!  They are so easily adjustable (Velcro), washable and lasted right up till my large breed puppies left for their new homes.  Less than a tenner for 12.  I'm no good at posting links but if you google them you will find them on Amazon, e bay etc.

Velcro ones here too. They are great and will go from birth to leaving home !!
Aileen