The Canon OC-E3 Off Camera Shoe Cord maintains all on-camera flash functions (including E-TTL II) for one Canon Speedlite used off-camera at distances up to 2' (60 cm). It is compatible with all Canon EOS cameras except the 630 and RT (which require a combination of TTL Hot Shoe Adapter 3, OA-2 Off Camera Shoe Adapter & Connecting Cord 60).
The OC-E3 has been improved over the OC-SC 2 with better sealing against dust and moisture, to better match the weather-resistant design of the EOS 1D Mark III and the 580EX2 flash. It also now features a sturdier foot.
Also fully functional with the combination of the T90 camera and 300TL flash (from Canon's older FD manual focus system).