Squish 18 Kids Bike, used but in good working order. From the Squish website:

"The Squish 18 is the perfect in-between size. Designed for kids aged 4 years and up, this bike provides the confidence they need to take their next step in cycling.

Weighing just 6.96kg, the lightweight frame makes handling and manoeuvring effortless. Keeping things simple, the Squish 18 features a single-speed drivetrain, allowing young riders to focus on balance, pedalling, and control before mastering gears. The 18” wheels and 9.5” frame are perfectly proportioned, ensuring a comfortable fit and smooth ride.

With grippy pedals, a child-specific saddle, and junior-sized handlebars, this bike is built for maximum comfort and control. Whether riding around the park or exploring new paths, the Squish 18 is the ideal confidence booster for your young cyclist!"

Sizing 

The 18" Squish bike is recommended for children aged 5+, with a minimum inside leg measurement of 50cm and a minimum height of 110cm (3'7").