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Home / All / Glass industry trends and buying guide / BK7 vs K9 Optical Glass: Which is Best for Optical Domes?

BK7 vs K9 Optical Glass: Which is Best for Optical Domes?

Apr 7,2026
Felix Glass explains the key differences between BK7 and K9 optical glass for custom optical domes. Both are high‑quality optical glasses, but they have distinct refractive indexes, durability levels, and cost structures.
 
BK7 glass has a lower refractive index (~1.51) and excellent transmittance across the visible spectrum. It is widely used for CCTV camera domes, underwater camera domes, and general optical applications. BK7 is cost‑effective, easy to process, and suitable for most standard‑performance requirements.
 
K9 glass has a higher refractive index (~1.52) and better optical clarity, making it a preferred choice for high‑precision applications such as aerospace domes, medical imaging lenses, and high‑end security systems. K9 is more stable under temperature changes and can deliver sharper imaging.
 
In summary:
 
- Choose BK7 for cost‑effective, standard optical domes
- Choose K9 for higher precision, clarity, and demanding applications
 
At Felix Glass, we provide custom sizing, AR/AF/AG coating, and full OEM/ODM support for both BK7 and K9 optical domes. Contact us for a free quote.
Learn more from our FAQ
Can you customize the samples style according to my design requirement?

Of course! We can customize the process according to your needs: shape cutting, AR AG coating, high temperature oven, polishing and tempering, anti-UV ink printing, based on our mature supply system for processing and customization

Can I get a sample with my own logo?

Since customized samples and shipping costs are high for both parties, in order to ensure a win-win situation for both parties and quality assurance, we only provide high-quality samples. But we can also provide existing product renderings and design mold services. Usually, we will first provide product renderings with your LOGO as a reference. Click to learn more about free samples

What is your Production MOQ?

The minimum order quantity for our factory production is flexible and negotiable. Usually the MOQ is 100 pieces, and lower quantity is acceptable for trial order. Please feel free to let us know the quantity you need.

Can I purchase your products in bulk? How is the MOQ?

Yes. Our MOQ is flexible and can be negotiated,Each variety starts at 100-500pcs.

How is the payment?

30% Deposit for order confirmation, 70% balance payment within one day before delivery.

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