Purchase it directly from the manufacturer PS.
SRS does not sell Active Belt from SRS website.
 
Must be purchased directly from the manufacturer.
http://www.pt-actuator.com/products/Active_Belt_Tensioner/2021/0202/322.html
 
Feel the power of sustained G-forces like never before. TensionR™ adds an extra level of realism for the ultimate racing or flight experience.
 
It comes with a 5 point belt system and it's fully integrated with Sim Racing Studio software for an easy, plug-and-race/fly experience
 
Setup and troubleshooting guide. https://simracingstudio.freshdesk.com/support/solutions/articles/35000189166-pt-active-belt-setup-and-troubleshooting-guide