Product review (5 stars): Genuine Whirlpool replacement for WFW9750WW01- fits and works perfectly.
Amazon says 5 stars means "Love it".  It's very hard to love a washing machine part.  This one isn't lovable, but it is an exact replacement, arrived in a sealed, legitimate Whirlpool carton, fits exactly, and is the same quality as the one that came off.  And, delivery was prompt.

Most folks have to change these because of a tear or chunk that comes off near the bottom.  The is happens because of the abuse that occurs when loading and unloading.  It's tempting to shove clothes in and yank them out.... we're all in a rush these days.... but that's the main cause of a damaged seal.  Be gentle while loading and unloading, and your boot will probably not be nearly as likely to tear.

Be forewarned that if your machine uses a teardrop looking trim ring, it's one of the parts that has to come off, and it's held in place by two curved grey plastic strips on either side of the door.  The trim ring is snapped in place, and it's very likely you'll break a few of the snaps.  Each of these rings is $30, and they're not available on Amazon.  In my case, a couple of them broke, but the teardrop trim seems to be pretty secure so I'm leaving it alone for now.

My machine is a WFW9750WW01 duet.  Most Duets are similar but there are some small differences.  Start by unplugging the machine.  The repair sequence is (a) remove lower front panel -3 screws, (b) remove top  cabinet panel, 3 screws located on the back of the washer  (c) remove trim ring (this is where the snaps break), (d) depress the blue tab and slide out the detergent dispenser, (e) remove two screws on either side of the detergent dispenser, (f) Unsnap the control panel and carefully fold it up over the top of the machine, no need to disconnect wires but ENSURE MACHINE IS UNPLUGGED--  if a wire shorts to the cabinet that would be a VERY expensive mistake, (g) open the front door and remove two screws that secure the door lock to the panel, (h) use needle nose pliers or a small flathead screwdriver to remove the spring clamp that secures the bellows to the front panel, being careful not to damage it, then detach the old bellows from the front panel, (i)  remove front panel, leaving door attached - 4 screws, (j)  loosen the worm drive screw clamp until you can get it out - don't damage this either, it needs to be re-used, (k) remove the translucent white detergent dispensing tube from the old bellows, again being careful not to break it since it's plastic, (l) look at the old bellow to be sure you are clear on how it fits, then remove the old bellow and discard, (m) clean up everything, especially the surfaces where the new bellows gets clamped into place.  Take some time and clean it well.  Any crud under there can cause a leak.  Now, reverse the steps to get the new one installed. Be sure to check that the new bellows is seating properly under both the screw clamp and the spring-loaded wire clamp.  That wire clamp comes off easy but can be a challenge to get on...extra hands are useful, and you will need to use a set of pliers or a visegrip to let you stretch the spring.  Be patient, be careful not to damage the new bellows with your tools, and don't overstretch the spring - stretch it just enough.  There are a lot of steps, so it will take a while to do this.  As mentioned earlier, the snap on plastic stuff is always problematic because after a few years the plastic gets brittle, so be careful.  If I had to do it again I would have those grey plastic curved snap strips on hand, but as mentioned mine seems be holding ok with a few of the tabs broken.  Good luck!  It's a very nice washing machine...definitely worth keeping in top shape.