The exact items included differ depending on which sizes you purchase. However, all you have to do is ensure that you are ordering the correct sizes for your frame and you're all good! The package will include an inner sleeve/pin, (2) IGUS bushings with o-ring seals, and several outer spacers depending on the size.  

Yes, because the shock eyelets are the same size. You just need to press out the metal DU bushings from the RockShox shock eyelets and then install the white plastic IGUS bushings included with the Fox hardware by simply pushing them in with your thumb. We recommend using a DU Bushing Removal Tool to quickly and easily press out the metal DU bushings.

In almost every case, yes you can install Fox mounting hardware into a different brand of shock. Eyelet sizing in rear shocks is pretty standardized these days, and almost every brand uses an eyelet with an inner diameter of 15mm and width of 12.7mm (1/2") which is what Fox mounting hardware is built for. If you have a modern shock, with an approximate model year of 2017 and newer, you can bet that the eyelet size is going to be the standard 15mm x 12.7mm eyelet size. This is absolutely true with all modern RockShox, Fox, DVO and Ohlins shocks.

However, some brands have used some different eyelet sizes in years previous to ~2017, so we recommend that you measure those eyelets with calipers to double check. And if your shock is older and dates back to the mid 2000's or older, we recommend measuring your eyelets to confirm your eyelet sizes no matter what.

While it may sometimes seem like the inner sleeve/pin from Fox mounting hardware will fit into a metal DU bushing most commonly seen on RockShox shocks, it will not. The sizing is very close, but not the same, and attempting to forcefully press together these mismatched pieces of hardware is absoutely not recommended. Fox designs all of their mounting hardware around fitment with IGUS bushings.

If you have a shock with metal DU bushings installed, you will just need to purchase a DU Bushing Removal Tool to press out the metal DU bushings and then simply push the new IGUS bushings into the eyelets. (2) IGUS bushings are included in each set of Fox mounting hardware.

 
If your mountain bike frame is specced for a 22mm wide mounting hardware such as m6x22, m8x22 or m10x22, you will notice that these are not options for the sizes of Fox Mounting Hardware.

In this situation you will simply order the 21.84mm width. Your frame will have enough tolerance to slightly squeeze together to accomodate for the slightly more narrow hardware. Do not order the 22mm width as the frame will likely not tolerate opening up to fit the slightly wider hardware.