Heater box...maybe I left a piece out?

Speaking of heater parts - I'm looking at the vacuum line set for the HVAC controls. Engine was out when I bought the car so so things I didn't get to see intact. The lines the run in to the engine bay, are they supposed to be stiff and connect with rubber couplers? Or are mine just hard from heat and age? They're pretty solid on the engine bay end, and I figured it could be either situation.