Quote Originally Posted by windly9 View Post
Hi, does anyone know if the midget size bulb(like M25) will be fit ok into a flash unit that usually uses bulb like P25 or GE 5 or another way round. Are they having same size in base and can they interchange with each other?

No. The base of the M-25 is smaller and different. There are adapters to use M series bulbs in flash units designed for #5 type bulbs. Also the #5 or Press 25 bulbs will not work in the M series flash guns. Press 25 or GE #5 bulbs were designed to work with five inch reflectors and the M series bulbs were for a three inch reflector. Changing reflector size can make a difference in guide number.