FSA ACR Spacer for Trek Emonda 2021+ Resin Black w/FSA Logo. Vision ACR spacers are precision-engineered components designed to integrate seamlessly with Visions aerodynamic cockpit systemsparticularly the Metron 5D ACR handlebars. These spacers serve as structural and aesthetic bridges between the handlebar and the frame enabling fully internal cable routing while maintaining a clean aerodynamic profile.