Level 0: can ride without training wheels.

Level 1: can ride parking lot, around playground

Level 2: can ride with parents on sidewalk and paved biking trails.

Level 3: can ride in town on bike lane, know signals and stop signs.

Level 4: can ride a bit 'off-road' in town, say grass on playground, dirt trails in the park. Can handle small bumps and drops. can do stand-up pedal. (recommended trails: Pinole point park. Sequoia bayview trail at Joaquin Miller park. )

Level 5: can handle bumpier off road, like China camp Shoreline trail.

Level 6: age 5 and up, can ride a 20-inch geared bike,