[Lifetime Warranty] 99944200903 Speed-Feed 450 Trimmer Head - Compatible with Echo SRM-266, SRM-266S, SRM-266T, SRM-266U, SRM-280, SRM-280S, SRM-280T - 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, 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.
• Other High-Capacity Models: SRM-3020, SRM-3020T, SRM-410U.
• Technical Fitment: Standard fitment is M10 x 1.25 LHF (Left Hand Female).

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.
• 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.
• Soak Your Line: To extend the life of your trimmer line, soak the spool in water for 24 hours. This keeps the nylon hydrated, making it more flexible and resistant to snapping at the eyelet.