Rotary Copperhead Mulching Mower Blades Fit John Deere Models D100 LA100 Replaces OEM GX22151 GY20850 For 42 Inch Deck (pack of 2)

What It Is

This is a set of two aftermarket mulching blades for 42-inch cutting decks, designed to replace OEM John Deere blades on D100 and LA100 series tractors. They are meant for mulching grass clippings into fine particles that decompose quickly, reducing the need for bagging.

Fitment & Compatibility

Before buying, verify your deck measures exactly 42 inches (blades are 20.5 inches long, 2.5 inches wide, with a 1-inch diameter center hole and a 0.25-inch offset). They fit John Deere D100, D105, D110, D120, D125, D130, D140, D150, D155, D160, D170, LA100, LA105, LA110, LA115, LA120, LA125, LA130, LA135, LA140, LA145, LA150, LA155, LA165, and LA175 models. They replace OEM part numbers GX22151 and GY20850. If your deck is stamped “42-inch” but is actually 42.5 or 40 inches, these will not fit. Check your current blade’s length and center hole diameter before ordering.

Key Things to Know

• Mulching vs. bagging: These blades have a curved, high-lift design that recuts clippings multiple times. They work best with a mulching plug installed; using them with a bagger may reduce airflow and cause clogs.
• Installation is straightforward but requires a torque wrench. Tighten the blade bolt to 70–80 ft-lbs (check your manual). Over-tightening can strip the spindle, under-tightening can cause blade ejection.
• Balance check recommended: Aftermarket blades sometimes have slight weight imbalances. Use a blade balancer or have them balanced at a local shop to avoid vibration and spindle wear.
• Sharpening frequency: These blades stay sharp longer than OEM but still need sharpening every 10–15 hours of mowing. Replace annually or if bent.

Should You Buy It

If you own a John Deere D100 or LA100 series with a 42-inch deck and primarily mulch your lawn, this is a solid, budget-friendly replacement. It’s not for bagging or side-discharge use, but for mulching performance at half the OEM price, it’s a reliable choice backed by strong user reviews.