If you want the legal answer + the popular answer:
Legal (CVC §26708)
- Front 2 doors: 70% VLT
- Rear side & back: any darkness
- Windshield: top 4-inch strip only
The popular setup
- Front 2: 70% ceramic (CA legal, blocks 60–80% of IR)
- Rear sides: 20% ceramic (matches factory privacy glass)
- Rear window: 20% ceramic
- Windshield: 70% ceramic full coverage (visor strip optional)
This setup gives you maximum heat rejection, keeps the car looking factory from the outside, and stays 100% legal in California.