| Tail Number / N-Number | N21SG |
| Manufacturer | CESSNA |
| Model | 421C |
| Year Built | 1976 |
| Manufacturer's Serial Number | 421C0039 |
| Aircraft Type | Fixed wing multi engine |
| Category | Land |
| Builder Certification | Type Certificated |
| Number of Seats | 8 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Engine Manufacturer | CONT MOTOR |
| Engine Model | GTSIO-520 SER |
| Engine Type | Turbo-prop |
| Number of Engines | 2 engines |
| Horsepower per Engine | 435 hp (325 kW) |
| Total Horsepower | 870 hp (649 kW) |
| Average Cruising Speed | 90 miles per hour |
| Type of Registrant | LLC |
| Owner Name | TWO ONE SIERRA GOLF LLC |
| Street | 3516 SW 110TH ST |
| City | SEATTLE |
| State | WA |
| Zip Code | 98146-1760 |
| Region | Northwest Mountain |
| County | King County |
| Country | US |
| Fractional Ownership | No |
| Airworthiness Classification | Standard |
| Airworthiness Date | 1984-04-18 |
| Certificate Issue Date | 2012-09-18 |
| Last Action Date | 2021-04-19 |
| Expiration Date | 2028-09-30 |
| Status | Valid Registration |
| Mode S Code | 50334300 |
| Mode S Code Hex | A1B8C0 |