The lower adapter for the UPPAbaby VISTA is needed for double stroller configurations involving an infant car seat or bassinet on the lower position.
It is not the same as the RumbleSeat adapter, which attaches the lower stroller seat and is included with your purchase of the RumbleSeat.
The upper adapters are also needed for configurations that use the lower adapter to create necessary space.
This adapter fits VISTA and VISTA V2 strollers from 2015-present.
Configurations with Vista Lower Adapters: