OS PRESSURE NIPPLE FS-90 This is a replacement breather nipple for the following O.S. engines -FT-120II FT-160 FT-300 FS-90 INCLUDES One breather nipple One plastic washer for nipple SPECIFICATIONS nipple thread size - 12-28 washer inside diameter - 3/16" outside diameter - 5/16" COMMENTS This breather nipple mounts onto the rear housings of the engines listed above.