The Shotgun Pro is the ultimate child seat for MTB families - zero frame contact, lightning fast fitting and removal Secure fitting to a wide variety of bikes including e-mtb's with bigger downtubes. In terms of bike compatibility, the Shotgun Pro fits all mountain bikes with standard 1 1/8 steerers, which is the vast majority of modern bikes. And so that MTB parents can share the duties, two headset spacers are included with the product – allowing for quick switching between bikes. The rear of the Shotgun Pro attaches to all common seat post sizes, and is dropper post friendly.