Max wt 250 pounds, size large with lateral supports and tray.
No harness, seat belt or headrest

https://www.rifton.com/pdfviewer?url=%2f-%2fmedia%2ffiles%2frifton%2fproduct-information%2frifton-hts-detailed-measurements.pdf%3frev%3d7432c97cb23b4f77b6becec1fdda8bf0%26hash%3dEBD112B8781FADD2F0D9F586EA514894&title=rifton%20hts%20detailed%20measurements