LAURI-OPEN-INSERT-100x22; for blades up to about 3 7/8" long ( up to 4" if the point is in line with the spine), and .085" wide. While the opening is nominally 22 mm wide, samples actually measured 21.5 mm., about 13/16".
Open inserts from Lauri; as the name implies, these do not completely enclose the blade. One side is left open to reduce bulk. Traditionally the open side is toward the back of the sheath to leave room for the stitching seam. They are quite flat, so they would be less bulky than the closed inserts. They are particularly suitable for the smaller knife in a two knife combination sheath.