Is this the one you got?
Brey Krause Roll Bar Extension 986 Boxster - Rennlist Discussion Forums
If so the side plates are in the picture and mounted to the bar (you will have to take at least one off to get it mounted and loosen the other one - it is easier to just take them both off) - if this is the one you have everything you need. Sweet price for $350.
Also, I have a roll of helicopter tape, PM me your address and I'll drop some in the mail to you so you can put the strip of tape under the BK bar to protect your OEM roll hoops, not really necessary if this is going to be a dedicated track car but if you ever plan to convert back to street this can protect the finish on the back of the hoops.