BMW Z4 [E85/86] factory strut tower brace, part# 51710305114, typically ~~$300.00
Attachment 362556
one reseller source...
Attachment 362555
Torque to 35 Newton-Meters for the nuts holding the brace to the the strut towers. Take care NOT to overtighten these nuts as you can easily snap the strut tower bolts.
Install manual:
Attachment 362557
RC.