Only difference in the d4 composite and the d4 TEXTREME Carbon, is the:
• Textreme Carbon shell is lighter/stronger/more expensive swedish carbon spread tow fiber, it is significantly more expensive than generic carbon weaves found on other helmets.
• D4 Textreme comes with a zippered pro bag, the composite comes with a carrying sock bag
They both meet or exceed all of the certifications that are standard in the DH/BMX race helmet market, both have the same amount of EPP and Made in the USA EPS in those helmets so energy management tests will be the same...Shells are different as noted with that Textreme being the pinnacle shell material, but, the composite carbon/fiberglass shell is ridiculously strong as well.