Tank, the 155 comes with that exact color cup in the box with it... I use it for detail and small jobs. While not exactly gravity feed it is still a blessing in that you can get down in lower pressures with it and use less paint for small jobs.
1. it's a lot less distance to suck the paint into the brush
2. there is some help by gravity in pulling down on the paint which allows a little assistance to get it into the brush...
but yeah, it acts a lot like gravity feed... not exactly but it makes it better... (p.s. all the siphon feed badgers come with this)