Product Overview
Splicing dog bone. - Blue Colour
Max outer diameter: 8mm
Length: 32mm
Min inner diameter: 5.5mm
Rope diameter: 4mm-5mm
Lacing eye: 2.5mm
Safe Working Load: 600kg
Breaking Load: 1100kg
Weight: 3g

how to see : https://www.allenbrothers.co.uk/2022/01/13/how-to-use-sailing-dog-bones/
These are spliced in a rope end and used to hold similar to a stopper knot or Diamond knot.