I'd venture to say if you have an older vehicle, especially an older pickup, we know all too well the havoc that moisture+time can wreak on all sorts of internal door components, despite good window seals. I just had a refresher course on that topic when replacing the side view mirror; decided since I had the panel off, why not do some cleaning and maintenance... pulled out some corroded butted MTX terminator 5.25, terminals, frame, all in sad sad shape. they were due for replacement, (passenger door driver suffered puncture wound beyond cosmetics)
To stay ahead of the elements and protect the fresh upgraded replacement speakers, I am using the 5.25 nix baffles in the doors of my '90 Jeep Comanche.
first impressions. the bolt pattern aligns great with stock speaker mounting, thumbs up.
the material feels like it will last many years. rubber baffle material also act like a gasket between the metal of the door and the driver. the back of the baffle leaves about an 1.5" gap between outer doorskin, where I placed the foam circle. it extends plenty far beyond the rear of a Kicker KSC5 driver, which is promising for protecting the rear assembly of the driver.
I treated the door with NVX 91mil thick damping material. one is treated, one is untreated. I will do a comparison of how the baffle performs in a damped door environment, Vs. undamped door environment. will report back soon
it should be noted that if the door panel doesn't allow for much space between driver mounting surface and inside of door panel, one may have to trim some of the material from the baffle mounting lip. test fit door panel before trimming the ring though!
if this^^ doesn't apply to your situation, the extra material acts to channel more sonic energy into the listening space, less lost to the voids of the back of your door panel.