SKS P45 Fenders: For 650b & 700c tires 28mm to 38mm
SKS fenders are our favorite fenders in the world. They're made of a gummy, recycled plastic that's hard to crack. They're less fussy to mount than most. They're quiet. They take to drilling and reaming and snipping and dremeling. They don't cost $100.
May 2019 update: The cream P45 colorway has been discontinued by SKS. Get it while you can.
For 700c tires skinner than 28mm: P35
For 700c tires 28mm to 38mm: P45 Longboards if you ride up to a 700x38 size.
For 650b or 700c tires up to 45mm: P50
For 26" tires up to 2" : P55.
For any 700c, 650b, or 26-inch tires 2" or fatter: B65
TIP: Get some reflective tape and run a strip of it up the back fender. It sticks great and shines bright, and if you're ever out at night without a light, at least you've got this.
TIP 2: After fitting and adjusting the fenders, you may want to trim the stays so they sit below the crown of the fender. It means breaking the stay, which you can do by severly crimping it with side cutters, then wiggling it to complete the job. Then
TIP 3: Most of the time these fenders fit without modification, but sometimes the fit is imperfect and they need home-surgery to clear a front derailer or chainstay or seatstay. Use side-cutters or snips of some sort to cut away the interferering plastic, then dremel or hand file the rough edge smooth. Add tough tape to cover it or leave it raw.If the stays that come with these fenders aren't long enough for your bike (unusual), then get the longer stay fender hardware kit here.