PET 801-10 #12 914 504 155 90 engine compartment seal
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rear seal 914.504.155.10 is shown as NLA. The profile of this seal is shown in the following picture on the right.
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I noticed that a seal used on a '77 911 looks very similar and is still available. The 911 PN is 911.504.111.02

I've also seen that a VW bug seal 111.813.705 D and/or C16-111-741 G (cip1 PN) are used for the rear engine compartment seal

I'm currently making these. This is actually one of my photos. I also make 2 versions of the 911 seals one is significanlty shorter, the other is not 100% correct as it is slightly shorter, but couls also be used.