Don't know.  I installed two of the thicker ones before someone on this list set me straight.  I believe the thicker one is for air-cooled or diesel or ...

Karl Wolz
Sent from my electronic umbilicus

On Jun 14, 2013, at 6:54 PM, Jeff Lincoln <magikvw@GMAIL.COM> wrote:

> Karl - that's what I installed the thicker one. I did counter sink it
> though per go ole' Boston Bob's video.
> 
> Why the thinner one? I picked the thicker one based on a big write up on
> the Go Westy site .
> 
> 
> --
> Thanks,
> 
> Jeff
> '85 GL (Gertie)
> '78 Bus (Melissa) Patty's Bus