Assembled Honeywell PS1202B12 power box for F300 F50F 12½ x 20 series one and series two with all internal components. It includes an air flow sensor, interlock switch, on-off switch, neon light, 60" power cord with 3-prong plug. The power box underside has the contacts for the two cells. Simple to install with two screws and then plug in. 

This power box has an overall size of 12½ x 6½ x 3½ inches.