Accuracy, reliability and affordability. There are plenty of precision measuring tool manufacturers who can hit two out of the three, but it is surprisingly rare to get all three at once.
Kinex are a small European manufacturer who focus their time and effort, and ultimately your money, on getting the metallurgy and working surfaces right.
All Kinex products are produced to German (DIN) industrial norms. As a general guide DIN 875/1 is equivalent to BS939 grade B for squares and DIN 874/00 is fractionally tighter than BS5204 grade A for straightedges.