Sugihara Ro-tsuke welded snaps are quite sophisticated snaps. Wires are all SUS H/B NI steel. Proudly made in Japan by artisans.

Snap length.
#00 7kg 8.3mm, up to 4lb nylon lines
#0 11kg 10.4mm, up to 8lb nylon lines
#1 20kg 12mm, up to 20lb nylon lines (stronger snaps)