If you have recently purchased a chamberlain belt-drive garage door opener or plan on buying, this an extension that you will need if you have 8ft garage doors. Compatible with Whisper Drive Plus Models,
The openers, that I have seen, come for 7 foot doors.
I purchased this previously and install was fairly straightforward. Normally around $60 and goes down to this price once or twice a year. Its been down for much cheaper a very long time ago, and maybe $1-2 cheaper than this periodically also.
First post, so please be polite. Got price, item, and retailer in title.