| Tail Number / N-Number | N121GK |
| Manufacturer | KURTZ GAROLD |
| Model | RV4 |
| Year Built | 2003 |
| Manufacturer's Serial Number | 2767 |
| Aircraft Type | Fixed wing single engine |
| Category | Land |
| Builder Certification | Not Type Certificated |
| Number of Seats | 2 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Engine Manufacturer | LYCOMING |
| Engine Model | IO-360-L2A |
| Engine Type | Reciprocating |
| Number of Engines | 1 engine |
| Horsepower | 180 hp (134 kW) |
| Kit Manufacturer | VANS AIRCRAFT INC |
| Kit Model | RV-4 |
| Type of Registrant | Individual |
| Owner Name | BOOK THOMAS D |
| Street | 2908 PRONGHORN CT |
| City | LOVELAND |
| State | CO |
| Zip Code | 80537-9068 |
| Region | Northwest Mountain |
| County | Larimer County |
| Country | US |
| Fractional Ownership | No |
| Airworthiness Classification | Experimental |
| Airworthiness Date | 2003-03-12 |
| Certificate Issue Date | 2021-08-19 |
| Last Action Date | 2021-08-19 |
| Expiration Date | 2028-08-31 |
| Status | Valid Registration |
| Mode S Code | 50054011 |
| Mode S Code Hex | A05809 |