SKU: 32455411855

537185801 Bump Knob - Fits Husqvarna T35 Trimmer Head (2003-05, 2005-01, 2007-04) - 4 Pack

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Description

537185801 Bump Knob - Fits Husqvarna T35 Trimmer Head (2003-05, 2005-01, 2007-04) - 4 Pack537185801 Bump Knob Replacement Key Features High Impact Blue Polymer: Manufactured from a high density, abrasion resistant plastic specifically designed to withstand thousands of high velocity "bumps" against asphalt, gravel, and packed soil. Reinforced Structural Ribbing: The internal geometry features reinforced walls to prevent the knob from cracking or shattering under the extreme centrifugal force of commercial grade trimmers. Precision Spring

537185801 Bump Knob Replacement

Key Features

  • High-Impact Blue Polymer: Manufactured from a high-density, abrasion-resistant plastic specifically designed to withstand thousands of high-velocity "bumps" against asphalt, gravel, and packed soil.
  • Reinforced Structural Ribbing: The internal geometry features reinforced walls to prevent the knob from cracking or shattering under the extreme centrifugal force of commercial-grade trimmers.
  • Precision Spring Seating: Engineered with a centered internal recess to perfectly secure the T35's heavy-duty spring, ensuring a consistent and responsive line-advancement "snap" every time.
  • Commercial-Grade Multi-Pack: This 4-piece kit provides a cost-effective solution for landscaping fleets and large residential properties, ensuring you always have a spare on hand to prevent downtime.
  • Snap-In Tool-Free Installation: Designed as a direct-fit replacement that clicks into the existing T35 housing by hand, allowing for rapid field repairs without the need for specialized tools.

Replaces / Cross-Reference Part Numbers

  • 537185801

Compatibility & Fitment

This bump knob is the standard replacement for the professional "T35" series trimmer heads. Key compatible models include:

  • Husqvarna 100/200 Series: 123L, 123LD, 225L, 232L, 232R.
  • Husqvarna 300 Series: 322L, 323L, 324Lx, 325L, 325Lx, 326L, 326Lx, 327LS.
  • Husqvarna 500 Series: 522L, 525L, 525LS, 525LST, 535LS.
  • Historical Production Dates: Compatible with T35 heads manufactured during the 2003-05, 2005-01, and 2007-04 production cycles.
  • Note: Specifically for the T35 head. If you have the smaller T25 or larger T45, this knob will not fit correctly.

When to Replace

  • Worn-Through Bottom: The center of the blue knob has ground down from pavement contact to the point where the internal metal spring is visible or falling out.
  • Broken Retaining Tabs: The plastic clips that lock the knob into the housing have snapped, causing the knob to fly off while the trimmer is spinning at high RPM.
  • Seized Mechanism: Significant buildup of dried sap, dirt, and debris has fused the knob to the internal spool, preventing it from releasing new line.
  • Rounded Indexing Teeth: The internal plastic "teeth" that click against the spool have rounded off, causing the head to dump all the line at once during use.
  • Visible Stress Fractures: White lines or cracks appearing in the blue plastic, indicating the material has become brittle and is prone to catastrophic failure.

Installation Tips

  • Clean the Housing: Before installing the new knob, use a stiff brush or screwdriver to remove all dried grass and mud from the locking slots and spring area to ensure a 100% secure lock.
  • Inspect the Spring: Ensure the internal metal spring is not rusted or collapsed. If the spring is weak, the new knob will stay "compressed," causing the line to feed uncontrollably.
  • Snap-Lock Check: Press the new knob firmly into the housing until you hear a distinct "click" on both sides. Give the knob a firm tug by hand to verify it is fully seated before starting the engine.
  • Manual Feed Test: With the engine off, press the knob in and pull the trimmer line manually to ensure the indexing mechanism is releasing the line smoothly.
  • Avoid "Riding" the Head: To maximize the life of your new knobs, try to avoid letting the trimmer head drag on the ground while trimming; only make contact with the surface when you need to advance the line.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 32455411855

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4.0 ★★★★★
Based on 25 reviews
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Product Reviews
A
Verified Purchase
Andrew B.
Boise, US
★★★★★ 5
UPDATED: Replacement works great
Color: 3000K Warm, Size: 1Roll x 16.4ft
FINAL UPDATE: Seller shipped new power unit and it works great now. The lights are really great and super easy to cut to size and use. UPDATE 1: Seller got in touch and is sending replacement power unit. Will update again once it arrives. I do really like the look of these and they did wonders for a dark park of my closet that has built-ins. ORIGINAL: Lights stopped working after about 6 weeks (beyond the 30 day return policy). Seems like the control unit died. Haven’t found any feasible way to contact seller or manufacturer. Will update review if anything changes.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 26, 2025
A
Verified Purchase
Aerdnua24
West Palm Beach, US
★★★★★ 4
Light it up!
Color: 3000K Warm, Size: 2Roll x 16.4ft, Color: 3000K Warm, Size: 2Roll x 16.4ft
I am very happy with these. They are easy to use. The only reason I am not giving a five star review is because the instructions and assembly weren’t the easiest. At first we could not get them to work. After looking through the reviews, one man told us that the -\+ were backwards and we tried what he suggested and they worked. I do suggest that because there are two light reels there should be two connecter boxes as well. We had to purchase two packages. Overall, We are satisfied with our purchase.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on January 9, 2026
C
Verified Purchase
Chris
Boise, US
★★★★★ 1
Quality just isn’t there
Color: 3000K Warm, Size: 2Roll x 16.4ft
Was very excited to receive this product because I had difficulty lighting op these LED strip lights, this looks like a package that had everything that I needed. First off, the strip lights themselves are very thin with wise and would look funny on my project, the adhesive backing did not stick at all once removed The touch sensor works great for about 10 minutes and then completely died, overall not impressed with the quality of this product, sending back
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 4, 2026
N
Verified Purchase
north80
Draper, US
★★★★★ 5
Excellent Cabinet Lights!
Color: 3000K Warm, Size: 1Roll x 16.4ft
Great cabinet lights. Easy to install and connect. The touch less control is handy and works well to dim and turn the lights on and off. Been using them for half a year now. No complaints.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on October 30, 2025
T
Verified Purchase
Thomas H Gilmore
Charlottesville, US
★★★★★ 5
Works great
Color: 3000K Warm, Size: 1Roll x 16.4ft, Color: 3000K Warm, Size: 1Roll x 16.4ft
works well
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 19, 2026

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