Mongoose Legion Kids Freestyle BMX Bike 20 Inch
- 20 inch wheels, single speed
- Hi-Ten steel frame, 20.25 inch top tube
- 25x9T gearing, 170mm chromoly cranks
- U-brake with alloy levers
- 34.4 lb bike weight
- 48 inch minimum rider height
Last refreshed Jun 21, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A single-speed freestyle BMX for an intermediate kid who rides parks, streets and dirt. It ships for home assembly, so budget time for the build.
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ASIN: B07G1HWG9PModel: Legion L20Category: Kids' Bikes
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Overview
Mongoose built the Legion L20 as a park, street and dirt freestyle bike with a Hi-Ten steel frame and tapered head tube. Removable brake mounts, a U-brake and wide aluminum rims with BMX tires complete the build.
The reason to look at it is the real BMX geometry and parts list, which means a young rider can learn tricks on a bike that is built for them rather than a toy. The limitation is weight and the one-speed drivetrain, which make it a poor choice for long pedaling rides.
Who it's for
A big kid who already rides confidently and wants to learn freestyle on a purpose-built frame gets the most from it. Small children, or anyone planning long road rides, will find it heavy and limited.
Pros and cons
- Real freestyle BMX geometry
- Removable brake mounts
- Wide rims with BMX tires
- Frame and parts warranties listed
- Single speed only
- Needs assembly out of the box
- Heavy for a smaller child
Performance notes
Wide tires and a rigid frame hold the bike steady when landing, and the short gearing gets it moving quickly from a standstill. With no suspension, the rider and the chromoly cranks take the impact of every drop.
Specifications
| Brand | Mongoose |
|---|---|
| Model | Legion L20 |
| Dimensions & fit | |
| Wheel Size | 20 incheshigher than 62% of 142 kids' bikes |
| Weight | 34.4 pounds |
| Minimum user height | 48 inches |
| Capacity & performance | |
| Number of Speeds | 1 |
| Age Range Description | Big Kid |
| Construction & materials | |
| Frame Material Type | Hi-Ten steel |
| Wheel material | Aluminum |
| Warranty & support | |
| Warranty description | 5 years on the frame, 1 year on parts |
| Other details | |
| Brake Style | U-brake with alloy levers |
| Bike type | BMX bike |
| Suspension type | Rigid |
| Is Assembly Required | Required |
Closest rivals on specs
Frequently asked questions
Can the brake come off the Mongoose Legion L20?
The description lists removable brake mounts on the frame, so the U-brake can be taken off. Check local riding rules and the rider's skill before removing it.
Does the Mongoose Legion L20 come assembled?
No. The listing says Is Assembly Required: Yes and that it ships ready to be assembled.
Is the Mongoose Legion L20 a mountain bike?
No. It is a rigid, single-speed BMX freestyle bike with 20 inch wheels and no suspension, built for park, street and dirt.