I had two of those, and they started leaking and sucking in air after several flights. A buddy of mine also had one leaking recently, causing the engine to surge in mid air. I have since stopped using them.
Now I only use these foolproof fueling thingies:
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http://www2.towerhobbies.com/cgi-bin...?&I=LXAHE1&P=7
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http://www.centralhobbies.com/Fuel/f...ngs/CHFLD.html