The Bontrager XXX & Pro Stem Blendr Mono Base can be used with both the Bontrager XXX & Bontrager Pro Stems. The Mono base allows the addition of one Blendr mount. There is also a Duo base available for two Blendr accessory mounts. Features Blendr works with this simple formula: Stem + Base + Mount. Add accessory. Bases for use with the XXX & Pro Stem Add any accessory mount (sold separately) for an elegant, integrated look