527556001 Mulch Plug Assembly for Ryobi RY40107, RY40108, RY40109, RY40170, RY40180, RY40190 40V Electric Mower

What It Is

This mulch plug assembly (OEM part 527556001) replaces the rear discharge chute on compatible Ryobi 40V electric mowers, trapping grass clippings inside the deck to be finely chopped and returned to the lawn as natural fertilizer.

Fitment & Compatibility

• Exact models: Ryobi RY40107, RY40108, RY40109, RY40170, RY40180, RY40190 (all 40V, 21-inch deck models).
• What to measure: Deck width must be 21 inches; the plug opening is ~4 x 6 inches.
• OEM vs aftermarket: This is genuine Ryobi—no fitment guesswork. Aftermarket plugs for these models often lack the rubber seal and latch alignment, causing clippings to leak.
• Check your mower: Look for a rectangular opening at the rear of the deck (behind the blade). If your mower has a side discharge chute, this plug won’t work—it’s for rear-discharge models only.

Key Things to Know

• Installation is tool-free: Push the plug into the rear opening until it clicks. The rubber gasket should seat flush against the deck—if it doesn’t, you may have debris blocking the slot.
• No blade change needed: Unlike some mulching kits, this plug works with the stock blade. For finer mulch, you can upgrade to a high-lift blade, but it’s optional.
• Clipping quality: Users report decent mulching on dry grass; wet or tall grass may clump under the deck. Run the mower at full throttle and overlap passes by 2-3 inches.
• Durability concern: The plastic latch tabs can crack if forced or if the plug is left on in storage. Remove it when not in use to avoid warping.

Should You Buy It

Buy this if you own one of the listed Ryobi 40V mowers and want to recycle grass clippings without buying a bag or side-discharge attachment. It’s a cheap, easy upgrade for lawn health—but skip it if you routinely cut wet or overgrown grass, as the plug will clog and leave clumps.