If these reproductions are built just like the OE mufflers, then they each have a flow rate of 175 sCFM. I have a pair of NOS AAR mufflers & in 2001, I brought one of them in to work when I worked for Dynomax/Walker & we flow tested one. Our head engineer brought the muffler to my desk after testing it & said "this is a PIG!" The OE mufflers have a body length of 20" give or take an inch. Dynomax has this style muffler in Super Turbo, but they are 14" long bodies, & they flow around 425 sCFM - HUGE improvement vs the OE Chrysler muffler design. (BTW - Walker may have been OE on these mufflers to begin with anyway, but they were built to control noise - they are quieter than the Dynomax mufflers). Anyway, these Super Turbos are available in both 2.25" & 2.5" versions.