These caps screw perfectly onto a water bottle, but when the bottle is placed in place in the steam cleaner it pops out after a few seconds allowing water to drain and not being sucked into the heating part of the vacuum cleaner will. Maybe the rubber O-ring is a bit too big. That's about all I can make out because I can push it down for a snug fit and then it gradually disengages from the bottom of the hole where the cap is inserted. Unfortunately I didn't keep my broken cap so I can't attempt to replace the O-ring on it. I could tape the water bottle but that seems like a pain as it would have to be re-taped every time the bottle needed to be refilled. Looking at the reviews I see that only one person had this issue so chances are the cap will work well for most buyers.
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