As mentioned, product hubs are allowed...technically. But sometimes product hubs get shot down by cynical hubbers in the hub hopper and won't even get featured. I've had well-written, balanced, useful, no-hype product hubs that didn't even get featured because some hub hopper folks voted it down.
How did I get it featured?
I switched the photo at the top (the professional quality pic of a pretty Chinese model) with the photo at the bottom (the low quality snapshot of some white girls) and VOILA! It got featured.
The self-appointed HubPages police can be irritating sometimes, but just roll with it.
Good luck! Writing thorough product hubs is definitely a great way to take your HP income to the next level.