Trapnsporting a baby in bike trailer? This is possible with a babyshell specially made for child bike trailers. Or a toddlerseat in bike trailer for already seated children to provide extra support. The babyshell or toddlerseat for in bicycle trailers are universal and fit any child trailer. You can also mount a babyshell in a child cargo tricycle. A babyshell and Toddler seat are universal and fit any child cargo bike.