The Multi-Function Shoe Adapter AD-E1 is developed to retain compatibility with existing Speedlites such as the Speedlite EL-1 , 600EX series , 580EX II , and more . This adapter is required before mounting these Speedlites onto the EOS R3 due to their rubber sealing design . Speedlites that do not have dust- and drip-resistance feature , such as the Speedlite 270EX , 430EX and 470EX series , can be mounted directly onto the EOS R3 .