You can prepare lower-level versions of spells with shorter durations.
Benefit: Only spells that have a duration of at least one minute (10 rounds) when you cast them can be cast as fleeting spells. A fleeting spell has a duration of one round per 5 caster levels or fraction thereof (minimum one round). Fleeting spells cannot also have metamagic feats added that increase their duration or save DC. A fleeting spell uses up a spell slot one level lower than the spell’s actual level (minimum 1st level). Unlike most metamagic feats, a spell prepared as a fleeting spell calculates its save DC using the new, lower spell level.
Example: Davor is a 9th level half–orc wizard with an 18 Intelligence. He prepares a fleeting hold person as a 1st level spell. When he casts the spell, it has a duration of 2 rounds, and a save DC of 15 (10 +1 modified spell level +4 Intelligence modifier). If Davor had prepared a fleeting quickened hold person as a 5th level spell, he would still calculate its save DC as a 1st level spell.
The Genius Guide To: Feats of Metamagic