I changed the weather seal of my old Z4 last year, see: http://www.z4-forum.com/forum/viewtopic.php?f=3&t=6432&p=1136924#p1136924doane2u said:The only real wear I found, that looked bad, was the rubber weather seal around the windshield is deteriorating quite badly with lots of cracks and the piece going across the top is completely missing. Is that a common problem on this year and something that is easy to repair DIY?
The weather seal was an original BMW part $28.61..... 8) partNr: 51317017021 https://www.parts.com/index.cfm?fuseaction=store.PartInfo&PartNumber=51317017021&VehicleID=194309&diagram=1918330&Title%3DBMW-SEAL
or
http://www.ebay.com/itm/BMW-51317017021-GENUINE-OEM-REVEAL-MOLDING-/151663659294