Access the official King of the Hammers Rulebook online, download the current 2027 Ultra4 Rulebook PDF and find technical documents and reference materials for Ultra4 USA competition.

Whether you’re building a vehicle, preparing for technical inspection or confirming a rule before race day, this is the source for current regulations and supporting resources. The online Rulebook currently reflects the 2026 version and is being updated for 2027.

The downloadable PDF has been updated to the 2027 Ultra4 Rulebook.

The online Rulebook currently reflects the 2026 Rulebook and is being updated for 2027.

Until that update is complete, use the 2027 PDF as the current rulebook of record.

Direct rule and tech questions to Tech@KingoftheHammers.com.

Please cite the rule in question with the page and item number from the Rulebook when emailing.

Used during tech inspections:

SFI rated head and neck restraints are required for all classes:

Direct rule and tech questions to Tech@KingoftheHammers.com.

Please cite the rule in question with the page and item number from the Rulebook when emailing.