It utilizes a section of baffle material to aid in flexing at the step area.
Ron is correct.....they (the original design) seem to all crack.
The redesigned version that Bengie refers to has been out for a while now and it seems to be doing the job on my plane after 5+ years of service.
You can find a variety of baffle material on the market and I think you'll find that using anything less than the reinforced material for this job would be a mistake. It needs to be flexible yet rather stiff.
With cracks in your existing fairings, you'll need to do some sheet metal work along with adding the baffle material so this will complicate the surgery somewhat.
Jim
