Baffles?

I have a 78 650. The prior ower was running staight pipes. I want to install baffle but not sure what size or lenght. I am running aftermaket pods and my main jets are 110 and pilet is 17.5 (not sur if you needed to know that or not). The headers/exhaust are 4into4. Any help would help a newbie out alot. Thanks!!!

got a picture of the pipes?

I will post them later tonight. but they look to be the same size as the headers and the stop around where the shift and rear brake are. the two middle go under the bike and the two outside run with the bike frame. i plan on extendend them to the rear tire and then kick them outward. i dont know if i need a certain size baffles or will any size baffles will do?

they need to match diameter of header pipes;)

what about the lenght? i have seen them all different lenghts. what is the diffenerce between a say 4 inch long baffle to a 6 inch baffle?