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Per-Io-Tor #1 and #2 are round with grooves. #1 is small and #2 is medium.
They are designed for root grooves and furcation areas.
Per-Io-Tor #3 is a spatula with eyelet and #4 is a spatula with ridges.
They are used on plane and convex approximal surfaces.
#3 is extra thin for very narrow interproximal areas, such as lower anteriors.
Per-Io-Tor #5 has a concave working surface for vertical use on convex buccal and lingual surfaces.
Per-Io-Tor #6 has a convex working surface for vertical or diagonal use on concave approximal surfaces.