There are a variety of Chassis Certifications that are currently in use on the dragstrip, and all of them have to do with the combination of weight and ET. If a car is lighter, it will need a different chassis configuration than a heavier car that runs the same ET and mph. This is why there are a variety of chassis certifications outside of the normal 8.50 and slower standard roll cage certs. These chassis certifications are determined by the SFI Foundation, which was started decades ago by SEMA and is now a completely separate organization.

Besides Chassis Certification standards, SFI also tests and approves safety equipment and race parts of all kinds to be safe for racing use.

The two chassis in this video are a 25.2 and 25.1 chassis respectively. Here is what that means. 

SFI Spec 25.1K Full Bodied Car Tube Chassis – 7.49 Seconds & Quicker; 2,800 lbs. Maximum
Effective Date: July 2, 2021

SFI Spec 25.2E Full Bodied Car Tube Chassis – 6.00 to 7.49 Seconds ET; 3,200 lbs. Maximum
Effective Date: July 2, 2021