cascading saw filters

hi every one,
when i was testing my trans unit i observe that two saw filters in cascade will give more rejection in stop band.

how it is possible? any one explain me this concept plz.......

thank you
regards
among

Explain the obvious?

In simple words let say you have 2nd order filter. it gives rejection let say 12dBper octave.
If you cascade two such filters the resultant filter is now 4th order filter( muliplication of transfer function to get the cascaded effect)
The result is 24dB rejection per octave which gives more rejection than a single filter