Baby On Bike. This great shaped helmet for your most precious passenger is designed to fit smoothly into most bike seats and trailers. The BOB helmet provides safety for your child even if they only ride along in the back seat. The BOB helmet has the Lazer Comfit3 Retention System for an easy to adjust and perfect fit6 vents to help keep the interior cool360 degree reflective material assures high visibility. Glue on (1-piece) constructionWeight: 277 g for a Uni-Size KidsSize: Uni-Size Kids 46-52 cm