showingo M170642 UC22008 42" Mulching Lawn Mower Blades Replacement for John Deere 42" Deck Riding Mower Zero Turn Mower X330 X350 X354 X370 X380 Z335E Z335M Z345M Z345R Z315E Z320M Z320R (2 Pack)

What It Is

This is a 2-pack of 42-inch mulching blades designed for John Deere riding mowers and zero-turn mowers with a 42-inch deck. They replace OEM part numbers M170642 and UC22008, optimized for grass clipping recutting and fine discharge.

Fitment & Compatibility

• Deck size: Must be exactly 42 inches (measured blade tip to tip). Do not use on 44" or 48" decks.
• Models confirmed: X330, X350, X354, X370, X380 (select series); Z335E, Z335M, Z345M, Z345R, Z315E, Z320M, Z320R (zero-turn). Also fits select 100-series (like D105, D110) with 42" Edge or Accel Deep Deck—verify your deck model.
• OEM cross: Replaces John Deere M170642 and UC22008. Aftermarket, not OEM.
• Measurements: 42" overall length, 1" center hole, 0.25" thickness, 3.5" blade width. Check your spindle bolt size (typically 5/8" or 3/4")—these blades use a 1" center hole, so a bushing may be needed if your spindle is smaller.
• Check before buying: Confirm your deck model number (stamped on deck), blade length (tip to tip), and center hole diameter. Measure old blade if possible.

Key Things to Know

• Quality: Made of heat-treated steel (Boron or equivalent), but some users report minor balance issues—check balance before installing.
• Installation: Moderate difficulty. Requires lifting mower, removing blade bolts (likely 15/16" or 18mm socket), and torquing to 40-50 ft-lbs. Use a blade lock or wedge wood block.
• Gotchas: Mulching blades have a higher lift curve than standard blades—may reduce bagging efficiency. Not for side-discharge use without a mulching plug. Ensure blade orientation (cutting edge faces upward when installed).
• Wear: Expect 25-50 hours of mulching life depending on debris. Sharpen or replace when edges round.

Should You Buy It

If you own a compatible John Deere 42" deck mower and primarily mulch grass (not bag or side-discharge), this is a solid budget alternative to OEM blades. Skip if you need bagging performance or have a non-standard deck spindle size—verify fitment first.