I called Shar about it many months ago. They told me that it was cancelled and not offered, even though I observed it still posted on their website (and indeed, it is still listed as of this date).
I opted for the KC Strings gated extension, which I had installed by my local luthier. I posted a detailed product review here: Product Review: KC Strings Gated Extension
Purchase price is comparable to the one listed on the Shar site. Your mileage may vary as far as cost of installation goes; depends on your luthier.
I love the KC Strings extension. Rock solid, trouble-free, and a lot of fun drawing out those pipe organ tones in the section.
Hope this helps,