[Lifetime Warranty] [2026 Upgraded] 99944200903 Speed-Feed 450 Trimmer Head - Compatible with Echo SRM-266, SRM-266S, SRM-266T, SRM-266U, SRM-280, SRM-280S - Replaces X047000940

99944200903 Speed-Feed 450 Trimmer Head for Echo SRM Series

Key Features

• Lightning-Fast Reloading: The patented Speed-Feed design allows you to reload the entire head with trimmer line in under 30 seconds without ever disassembling the housing.
• High-Capacity Professional Spool: Designed to hold up to 20 feet of 0.095" diameter line, providing extended run times for commercial landscaping and heavy-duty residential clearing.
• Smooth Bump-Feed Advance: Features a heavy-duty internal spring and balanced centrifugal design for reliable, jam-free line advancement with a light tap on the ground.
• Universal Compatibility Hardware: Includes multiple arbor adapters (studs and nuts), making it a versatile replacement for most straight-shaft trimmers beyond just Echo models.
• Debris-Shielded Internal Gears: The internal indexing mechanism is sealed to prevent dirt, sap, and fine grass from entering the head and causing the "bump" action to stick.

Replaces / Cross-Reference Part Numbers

• 99944200903
• X047000940
• X047000941
• 78890-21001 (Shindaiwa)
• 102-565 (Stens)

Compatibility & Fitment

This "450" series head is the heavy-duty upgrade for Echo's professional-grade straight-shaft trimmers. Key compatible models include:

• Echo SRM-266 Series: SRM-266, SRM-266S, SRM-266T (High Torque), SRM-266U (U-Handle).
• Echo SRM-280 Series: SRM-280, SRM-280S, SRM-280T, SRM-280U.
• Echo High-Capacity Models: SRM-3020, SRM-3020T, SRM-410U.
• Shindaiwa Models: T260, T261, T270, T272, T282, T344.
• Note: Standard fitment is M10 x 1.25 LHF (Left Hand Female). Use the included adapters for other shaft sizes.

When to Replace

• Worn-Through Bottom Cover: The bottom of the head (the bump area) has ground down from contact with pavement or soil, potentially exposing the internal spool.
• Cracked Outer Shell: Visible stress fractures in the black housing, which can lead to the head shattering or throwing internal parts at high RPM.
• Line Won't Load: The internal "eyelets" no longer line up or the reloading mechanism is jammed with dried sap and debris.
• Excessive Vibration: The head has become unbalanced due to uneven wear or missing internal components, leading to potential gear-head failure.
• Eyelet Failure: The metal line exits have fallen out or are deeply grooved, causing the trimmer line to snap off inside the head repeatedly.

Installation Tips

• Left-Hand Threads: This head is Left-Hand Threaded. To install, turn the head Counter-Clockwise onto the gear head shaft.
• The Loading Arrow: To reload, rotate the top of the head until the arrows on the knob align with the metal eyelets. Push a single 20ft piece of line through until it comes out the other side evenly.
• Winding the Line: Once the line is centered, simply twist the top knob. The head will automatically pull the line inside and wind it perfectly on the spool.
• Gear Head Maintenance: While the head is off, check your gear head for old grass buildup. It is also the perfect time to add Lithium Grease to the gear-head port to prevent overheating.
• Locking the Shaft: Use a small hex key or screwdriver to lock the trimmer's gearbox before trying to unscrew your old head. If the old head is stuck, a pair of large channel-lock pliers may be required.