Diffusers/ashcatchers

I'm thinking of investing in a diffuser downstem and ashcatcher for my bong. I'm definitely getting an ashcatcher, but I am not 100% sure on the diffuser (just because i don't know what length i need and i dont wanna be out 20 bucks online if i get the wrong size)

i am putting em on this bong
12 inch Beaker with Ice Catcher

are they worth it? how much better is it with an ashcatcher/diffuser?

illadelph ash catcher is the only way to go. iv had 3 different ones and im telling u should save and get the 2 chamber illadelph. it ownss big time

id get the diffuser first, because diffusers make the hit waaay smoother