This bumper is meant to fit a european AtomicZombie "Bandito" build with 30x40mm square tube. Documentation of my build starts at: https://burningbecks.wordpress.com/2022/05/10/short-wheelbase-recumbent-bike-pt-1/ Original Bandito build tutorial: https://www.atomiczombie.com/tutorial-bandito-swb-recumbent