FISCHER Sprinkler Clamp FRSP C pipe clamps are offered in a range of diameters, from ¾ in. to 6 in., with bolt sizes of M10 or M12 and lengths up to 267 mm. Examples include 4‑in. × M10 × 195 mm, 6‑in. × M12 × 267 mm, 1½‑in. × M10 × 99 mm, and 2½‑in. × M10 × 141 mm. These clamps provide the variety needed for most sprinkler piping assemblies.