The Canon Speedlite 155A is a compact automatic flash unit featuring two automatic flash ranges plus manual. It features thyristorized circuitry for long battery life. Weighting just over ten ounces. Guide Number: 56. Recycling Time: 7 seconds w/Alkaline-Manganese batteries 5 seconds with NiCd batteries. Flash coverage: 35mm. Number of flashes: 300 or more with Alkalines and 90 or more with NiCds. For use with A series and the Power Winder A.