42 Inch Deck Mower Blades Fit for John Deere Z315E Z320M Z320R Z335E Z335M Z345M Lawn Mower Replaces OEM M170642 UC22008 M170639 GY20683 (Mulching) 2 Pack

What It Is

This is a set of two 42-inch mulching blades designed for select John Deere Z300-series zero-turn mowers. They replace OEM part numbers M170642, UC22008, M170639, and GY20683, and are intended for cutting grass and mulching clippings back into the lawn.

Fitment & Compatibility

Before buying, confirm your mower has a 42-inch cutting deck. These blades fit John Deere models Z315E, Z320M, Z320R, Z335E, Z335M, and Z345M. Measure your existing blade length (end to end) and center hole size (should be 1-inch diameter). Check that your blade bolt pattern matches—these use a standard 5-point star center hole. They are not compatible with 48-inch or 54-inch decks, nor with standard lift or high-lift blades from other brands.

Key Things to Know

• Quality: Aftermarket blades; 8 reviews show 4.8 stars, but inspect for consistent edge sharpness and balance out of the box.
• Installation: Moderate difficulty—you’ll need a socket wrench, torque wrench (recommended 70-90 ft-lbs), and a blade removal tool. Always disconnect the spark plug first.
• Common gotcha: Mulching blades have a curved, serrated edge; do not confuse with standard lift blades (which have a flat, angled lift). Using the wrong type reduces cutting performance.
• Durability: Made from hardened steel, but expect faster dulling than OEM blades if mowing sandy or rocky terrain.

Should You Buy It

If you own one of the listed John Deere Z300-series mowers with a 42-inch deck and want a budget-friendly mulching blade set, this is a solid choice—just verify blade length and center hole size before purchase, and be prepared to sharpen or replace more frequently than OEM equivalents.