I love the one I use, but don't need this new one as a spare so:
Selling for $150:
New-in-Box Backscatter AirLock Underwater Housing Vacuum and Port Lock System
Free First Class shipping anywhere in the USA.
Retail Price is $324.
*Please note* that if your housing doesn't all ready have a Backscatter housing bulkhead, you will need to buy one (cost is $75 from Backscatter)
