IMHO as someone who's done a fair amount of 1st AC work with follow focus rigs ranging from the jag35 one pictured (and similar super-cheap ones) up to very very expensive Preston remote rigs:
If you are looking at just about anything at the Red Rock Micro price range or below, you might as well just get the Jag and save your money for a nicer Chroziel down the road should you continue to do your own shooting and end up with a rent-able package.
I hate the cheap ones, on any lens (caveat below) The Jag unit has the same internal parts as the version 1 Red Rock Micro. They both have the same level of stiffness and slop in the gearing. The version 2 of RRM's is better, but not by enough that it warrants the price difference, with an asterisk.
Caveat: I don't feel enough a measurable difference in follow focus performance until the prices are high enough that it doesn't make sense for the indie filmmaker. Below a grand, there all pretty much the same from what I've experienced.
Asterisk: EF lenses and their stupid stupid stupid focus rings that have zero friction and no hard stops at close or infinity focus are so worthless for focus pulling and measuring marks anyway that you might as well get a decently made budget FF unit and wing it as best you can.
For example, in order to spin a 35mm L series canon prime from close to inf you usually have to exceed a 360 degree turn on the FF wheel. Infuriating. I'm sure if I had the time to sit down and make changes to gear pitch and not have gear rings like the one pictured (which drastically increase the circumference of the lens, and therefore increase the degree of turn on the FF wheel) I might be able to get it under 360, but that never happens.
I think the nicer units are really only cost effective if you've got manual lenses with some feel to them and hard stops to work with. You know, ones that won't breathe when you pull. Or if you are a shooter, getting a day rate and a kit fee for all that expensive gear.
Crap, now I'm late. Fortunately, not critical.
HTH.
