Microline - Clack Filter Housing Spanner Wrench - Fits standard Microline and Clack Systems. #3072. Only for use in loosening filter housings, never to tighten. Overtightening may cause damage to the O-rings and make re-opening VERY difficult. Hand tighten only. For really stubborn filter housings our technicians will use two wrenches together for maximum power where one wrench might break or not do the job when opening stuck filter housings. Place the handles of two wrenches pointing in opposite directions, use both hands and it will apply force evenly. Two filter housing wrenches work better than just one. Our techs know the tricks.