Lippert makes several versions of two different size under chassis storage bins.
The overall length of the framework is different between TH's and non TH's. Roughly 99" or 96"
3 versions for toy haulers, 27" long bins, with and without a spare tire carrier, and 48" long bins.
IIRC they only make one version for non toy haulers, and that is with 27" bins.
Here is the short and long version on our Cyclone. The short version with the spare tire carrier use be standard equipment. But one of the upgrades not long after we got ours was the elimination of these very handy bins.
Lipperts under chassis storage bins
I would not order them from Lippert, they only truck freight them.
Amazon lists them frequently with free shipping.
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=lippert+storage+bins
I will be selling the parts I did not use now, which would make a set for a toy hauler or standard trailer for someone that can cut and weld.