Canon Speedlite 420EX is a powerful flash guide number of 138. It features TTL compatible with all Canon EOS bodies and E-TTL features with some Canon EOS bodies; AF Assist Beam All ELAN 7 points; Wireless Triggering; Swivel head for bounce flash photography. The Canon Speedlite 420EX measures 2.8 W x 4.8 H x 3.9 D in. and weighs 10.6 oz. (without battery).