The PocketWizard AC5 RF Soft Shield for FlexTT5 is an enhancement for the FlexTT5 (340-354 MHz FCC models) radio transceiver when used with the Canon 430EX, 580EX and 580EX II Speedlites--the AC5 reduces radio frequency interference which can limit the performance of the FlexTT5. The AC5 provides a simple, elegant solution this situation.