<p>In order to build durable and sustainable prestressed concrete bridges and structures, preventing the steel components and the tendons from corrosion is key. Accordingly, for bridges with internal bonded post-tensioning, polymer duct systems should be used. The article gives an overview of the 50-years history of plastic ducts in post-tensioning, the selection of tendon protection levels (PL’s) according to <i>fib </i>bulletin 33 [1] and information for structural engineers regarding design and detailing of concrete structures with polymer ducts according to <i>fib </i>bulletin 75 [2].</p>