Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: I have Canon 7D and speedlite flash 550EX . Does this ST-E3-RT compatilbe with my Flash?
Document: This device Canon ST-E3-RT Speedlite Transmitter should have every photographer using flash Canon EX-600 RTI already like to use it.
I do real estate photography with off-camera flash units; I went with a 30' cable initially for the master speedlite because it was a lot cheaper, but you do get what you pay for. After 8 months of frequent use the cable ceased to work, plus I pulled a light stand down to the floor more than once. The ST-E3-RT made my life a lot easier, functioning exactly as described, and perfect for controlling the speedlites that I use for interior shots.
It's an in-camera external speedlite menu item at the bottom of the menu options.) The 600EX-RT gives you the same master transmitter controls as the ST-E3-RT, but in addition you get the autofocus assist beam, a backwards compatible optical transmitter capability, and a flash bulb. For just a little bit more in price.I've also heard a few people in the industry comment about the placement of the screen facing upward rather than to the rear.
I have been using Speedlite Transmitters for a while. The drawback to the ST-E2 was you need line of site for infra-red triggering.This is a pain when you can not align camera and flash. This ST-E3 solved this problem for me. For example at Christmas I was able to place the flash behind someone and get a hair light. With the ST-E2 that would not have been possible.Be warned:  this is not a simple unit to set up.
I have 3 600-RTs and the ST-E3-RT means I can use all 3 off camera and control all the features on each flash remotely from either the transmitter or from the in camera menus no more climbing up to or lowering flash units to make adjustments I love it.
The ST-E3-RT transmitter is a great adjunct to my 3 600RT flash units. It works especially well when I need to photography large groups and separate the flash unite for even coverage.The only possible downside is that it does not emit an IR focusing beam like the 600's do the 5Diii needs to have enough ambient light to focus on its own. Not a biggie, but buyers should be aware of that.
My business partner and I used this to photograph a difficult subject in my garage... a Zombie... no really, this thing worked flawlessly! The ST-E3-RT is the perfect addition to your lighting setup for photographing a difficult subject. All too often we find ourselves fumbling with flash settings when shooting wirelessly while our subject grows more and more irritated. No longer is that the case!This Transmitter transfers TTL settings to the Flash beautifully and out performs any radio transmitter I have used.
I love this little rascal. It works every time I push the shutter button, unlike the Nikon off camera system which depends on the mini flash built into the camera and unlike the Pocket Wizard which has a tendency to misfire just when I have the facial expression I want. The ST-E3-RT is compact and light thanks to its lack of a AF assist light and battery. I like it that way although it is of apparent concern to some photographers who would like to use it in very low light.
Yongnuo even reverse engineered this by creating their own model, the "YN-E3-RT". BUT - they added the AF Assist beam that everyone wants and GR mode works for pre-2012 camera bodies! Really Canon? This is a no-brainer. Skip the ST-E3-RT and wait for Canon to release the ST-E3-RT Mark II update that also includes the autofocus assist beam and the legacy optical transmitter functionality.
I don't even know why I didn't buy this trigger long time ago. I use it every day. I love this ST-E3-RT. People who give bad reviews about this trigger they don't know what they are talking about. lol
Answer: Nope. It only works with the canon 600 speedlite series. Although the 600 series can fire the 500 through its infrared sensor. Hope this helped you.