Ditch the batteries, and plug in.
Offering 500mA of current, the Outlaw 9V Power Adapter will power most guitar effects pedals - even digital units that draw higher current levels. It features a standard 2.2 mm plug (center-negative). Combine with the Outlaw Daisy Chain extension cable (sold separately) to power up to five pedals with a single PSU.
Be sure to double-check the voltage/current requirement specs of your pedal(s) to ensure compatibility.
Be sure to double-check the voltage/current requirement specs of your pedal(s) to ensure compatibility.