I've been detailing my car since 1995.  I've used quite a few wheel cleaners during my time and this is probably my favorite.It is my favorite because it does the job well and it doesn't suffer from any of the negative aspects of some other wheel cleaners.Griot's Wheel Cleaner is not a spray-on hose-off product.  With this product, you spray it on, agitate it, and then hose it off.  Griot's includes a yellow sponge with your order which is nice.  Personally, I recommend buying their lambskin wheel mitt as it is more effective.  I actually use this product with Griot's short-handle boar's hair brush and I finish up with one of the green three-finger detail mitts.  I don't like any other detail tools for the wheels.  Griot's sells a stiff foam brush with a black handle. I've used that and it is ineffective and a waste of money.The Griot's Wheel Cleaner obviously removes the brake dust effectively.  The reason why I like it is because...1.  It doesn't have a strong chemical smell.2.  It does not irritate your skin.3.  I believe it is also environmentally friendly4.  It doesn't damage any painted surfaces both inside your wheel well and on your car.Here are some of my tips to make this product work effectively...First, always work on a cool wheel. Then, spray just enough product on the wheel so that the mist coats the whole wheel.  There is no need to waste product.  Now here is the trick, make sure when you start to agitate the wheel with either the boar's hair brush or another brush or mitt that the tool is dripping wet.  Don't use a dry tool on the wheel as it will just soak up the Wheel Cleaner and work ineffectively.  The extra water helps lather up the wheel.  Do one wheel at a time and work quickly with fast movement. Then hose the wheel down and follow up with a green detail mitt if anything is left behind.  The key to the Wheel Cleaner is to get good lather.This is one of my favorite products from Griot's Garage. I've actually never used P21S wheel cleaner because of the price and shipping charges.  I've heard some people say that the Griot's product works just as well if not better.  IMO, I don't see how a wheel cleaner could work any better than this product. The only wheel cleaner that I ever liked that was sold in an auto parts store was the Turtle Wax wheel cleaner because it was non-alkali based.  If I was desperate for a wheel cleaner, I would use that.  If I had choices, the Griot's Wheel Cleaner would be my first.Griot's now makes several other wheel cleaners for specific wheel types.  I think the Wheel Cleaner is a great general purpose wheel cleaner and you will be very happy with it. 35oz should last you a good while depending on how much you wash your car and if you use it conservatively. If you have a car that suffers from heavy brake dust and you like to keep your wheels clean, then you probably should invest in the gallon size. Griot's now makes a foaming sprayer and I just might pick that up as it seems more appropriate for this product than a misting sprayer.I highly recommend this product.