Rockshox started in 1989 and was an instant hit, bringing scaled-down motorcycle forks to mountain bikes. In 2002 they had hit hard times and were eaten by SRAM, along with a few other legacy companies like Sachs and Avid. SRAM has kept Rockshox as its own line, unlike Avid, Huret, or Sachs, for instance, which were fully metabolized. Rockshox pretty much has two categories of forks. One line is the fully-serviceable, upgradeable line where all the premium stuff lives. These bottom out about $500 with the Reba and Revelation.

We are going to be talking about the cheaper stuff, from <$200 to $450, which currently includes...
28mm stanchions: Paragon Gold
30mm: 30 Silver, Judy, Judy Silver TK, Judy Gold RL
32mm: Recon RL, Silver TK, Silver RL, Gold RL
35mm: 35 Silver and 35 Gold

These forks appear mostly on mountain bikes, up to a pretty high spec (here's a $3200 Salsa that has a 2020 Sektor which for reasons unknown is same as a 2021 Recon Gold... but it deserves a Reba, same performance but the Reba could upgrade) and on a few nicer hybrids. Some of them are OEM-only, you can't buy them all at retail. These are different sizes, and provide a few different options for the travel, brake, and steerer. But for this discussion, they all work the same way. The 35 models are the newest in this family and present a heavy duty option for e-MTB's.

The naming conventions are not entirely consistent. But generally...

• The Gold versions all have aluminum stanchions, while the Silver and no-metal-name have steel.
• Some of the Silver or no-metal-name models have a coil or air option, while the Golds are air spring.
• The TK, no-metal, and Silver models have the Turn Key compression damper with no adjustment, just open and locked
• The RL and Gold versions have the Motion Control compression damper which gives a range of adjustment from open to locked.
• Rock Shox used to call all of the cheap air fork springs Solo Air, but lately they have started using the Debonair name too.
• Unlike the better forks, these have no part numbers in the catalog for the uppers and lowers. Chassis damage like a dent or a really bad scratch in the stanchions is therefore a new fork..

The air spring seems easy to understand but hides some fun complexity. The distinction between Solo Air and Debonair is not clear, because at first glance they did not change the upper piston design. They all use a valve in the piston that opens at top-out to equalize the positive and negative chambers. This allows the fork to reach zero force at top-out instead of slamming into a bump stop. But it seems like the Debonair versions have provisions for volume tokens, and have a seal in the bottom plate of the air spring rather than a floating piston. Either way, they all have one air valve. Travel spacers go in the negative chamber between the seals. In some of these forks you can add tokens - pieces of rubber that press onto the air valve and take up volume in the positive chamber, so the volume ramps up faster, acting like a higher spring rate in spite of starting at the same or lower pressure.

The rebound damper is in the right piston. It's a check valve. Going up, it's wide open and provides no resistance. Going down, the check valve closes and oil passes through the small holes. The rebound is adjustable on all of these forks, so far as I know. That's important given that adding pressure changes the spring rate, and the rebound must change to match.

The compression damper is an assembly threaded into the top of the right stanchion and it uses the oil displaced by the incoming piston shaft. Again, it's a check valve, directed through small holes going up and wide open running out. These forks all have Turnkey or Motion Control. The big difference between them is that Turnkey has two settings, open or locked, while MoCo has a range of low speed compression adjustment from open to locked. There were once fancier versions of these dampers, but in recent years they have been replaced in premium forks by the Charger cartridge damper, and simplified for these cheaper ones. There's a small volume of air above the compression damper to take up the volume of oil displaced.

Because of the variety of sizes needed for the different travel and stanchion diameters and thicknesses, the internal plastic parts are not usually interchangeable between forks, even though they are doing pretty much the same thing in all of them.

There are a few major things that separate these from the more expensive Rock Shox forks and other brands - but that also likely don't matter for commuting. Probably the biggest is that better forks have dampers that use a stack of spring steel shims that deflect under oil pressure, so that the force vs shaft speed can be designed and adjusted with more control. More expensive forks also commonly provide more knobs to turn, especially high speed compression. The air spring in the nicer Rock Shox forks uses a dimple in the stanchion where the piston tops out to equalize. This is better because it makes a consistent negative volume shared by every fork. It's also simpler and probably cheaper to make, but it's definitely lighter, so $$$. Travel change requires a different air shaft instead of spacers. Some other fork brands use three air chambers, allowing tuning of every point in the spring curve. Rock Shox does not, but there are aftermarket parts that do it. And of course the more expensive forks have all the usual bike part tricks applied to add lightness - stronger alloys, butted tubes, in a few places carbon fiber. Finally, there are very long travel options, and some really heavy-duty forks for downhill, like the Rockshox Boxxer and Fox 40.