Description
Practical value and everyday use
Troy Lee Designs D4 Poly Headliner; Solid Black XS (54CM) is listed in Helmet Liners. For a practical buying decision, start with this source-backed point: Replacement headliner for the Troy Lee Designs D4 Helmet.
The source also records: Yes. We offer a full range of replacement parts, including visors, padding, and more. Use this additional stated detail to judge day-to-day usefulness and package value: Application note: Details make the D4 the most coveted full-face in mountain biking, including MIPS C2 brain protection, an air intake system for ventilation, and an unmatched anatomical fit.
Value-focused decision
Compare those stated features and included items with the current on-page offer and the exact quantity needed. No performance claim is added beyond the source product record.
Complete source-backed product details
Product Description
D4 Bike Helmet
The reigning king of full-face helmets, the D4 range expands with a Polyacrylite model packing the same safety and comfort features as the premium carbon and composite models into a price-conscious shell. Details make the D4 the most coveted full-face in mountain biking, including MIPS C2 brain protection, an air intake system for ventilation, and an unmatched anatomical fit.
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Troy Lee Designs
D4 Helmet: Legend Redesigned
The Daytona Helmet changed everything. It’s the most iconic, most storied, and most chosen Downhill, Freeride, and BMX race helmets in bicycling history. First introduced in 1996, the legendary Daytona lead the modern era of mountain biking and BMX with a magical blend of style and innovation. The Daytona and its successors have been worn by more MTB and BMX heroes—and have collected more titles, medals and accolades, and YouTube views than any other helmet in history.
The video showcases the product in use.The video guides you through product setup.The video compares multiple products.The video shows the product being unpacked. -
Troy Lee Designs
D4 Helmet: Highlight Reel
The most iconic, most storied and most chosen Downhill, Freeride and BMX race helmets in bicycling history. The Daytona Series changed everything.
The video showcases the product in use.The video guides you through product setup.The video compares multiple products.The video shows the product being unpacked.
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What is MIPS ?
MIPS is a safety technology that adds a low-friction layer inside the helmet that can move slightly during an impact, helping to reduce the rotational force on the head and lowering the risk of brain injury.
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Can I purchase helmet accessories and parts separately?
Yes. We offer a full range of replacement parts, including visors, padding, and more.
Source product highlights
About this item
- Replacement headliner for the Troy Lee Designs D4 Helmet.




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