M170642 Lawn Mower Blades for 42" Deck, Compatible with John Dee-re Z315E Z320M Z320R Z335E Z335M Z345M Lawn Mower, Replace UC22008, M170639, GY20683, 2 Pack

What It Is

This is a 2-pack of aftermarket 42-inch deck lawn mower blades designed for John Deere Z300-series zero-turn mowers. They replace OEM part numbers UC22008, M170639, and GY20683, and are intended for mulching, bagging, or side-discharge cutting on 42" decks.

Fitment & Compatibility

Before buying, confirm your mower has a 42-inch deck (not 48" or 54"). These blades fit John Deere Z315E, Z320M, Z320R, Z335E, Z335M, and Z345M models. Measure your existing blade: length should be 21 inches, center hole diameter 1 inch, and thickness 0.25 inches. They will not fit older Deere decks or non-Z300 series machines without adapter kits. Always check your mower’s model number under the seat or on the frame.

Key Things to Know

• Quality: Aftermarket steel may dull faster than OEM (UC22008). Expect 20–30 hours of cutting life before sharpening, depending on turf conditions.
• Installation: Easy DIY job—remove spark plug, lift deck, use a 15/16" or 5/8" socket (check your blade bolt size). Torque bolts to 70–90 ft-lbs.
• Balance: Aftermarket blades may need balancing out of the box. Use a blade balancer to avoid vibration and spindle damage.
• Gotcha: These blades are not compatible with John Deere’s “MulchControl” kit—they lack the necessary notches for the kit’s baffle.

Should You Buy It

Buy these if you have a Z300-series 42" deck, want a budget-friendly 2-pack for seasonal replacement, and don’t need OEM-grade longevity. Skip them if you demand maximum durability or require exact OEM fitment for a MulchControl system.