Holder for any Velox EXP guard cartridge and Scepter 1.9um guard cartridge. Free-Turn architecture lets you change cartridges by hand without breaking inlet/outlet tubing connections—no tools needed. Includes 2 Titanium/PEEK hybrid ferrules (1 for the EXP stem going into the column) and 1 hex-head fitting (1/4") for connecting the SIL outlet tubing to the EXP inlet with the second ferrule. For replacement ferrules, use 220-91522-33 (single) or 220-91522-34 (10/pk). Equivalent to 227-31170-01.