Need Help with Mr Heater 4" Adapter for CAT3 piping

[Skip707]

Does anyone know what heater adapter I can buy to connect cat3 single wall 4" pipe to my Heater? I purchased the Nova Vent 4" CAT3 pipe but there adapter requires 1.75" of pipe insertion and there is only 3/4" pipe sticking out (pic attached). I found an adapter made by Sterling called a GG HEATER ADAPTER (pic attached) but was told you can't mix brands. Any help would be appreciated.

 

[moserjj]

I used this

Saf-T Vent[emoji768] 4" Rheem Appliance Adapter Category III Venting at Menards https://www.menards.com/main/p-1444453724796.htm

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