In the chat area this topic came up, I had a set of 5 1/4" comps to put in, Matt mentioned about going with 6 1/4's coaxials. Curiousity got the best of me, went and bought a set, they speaker already had holes to fit a 5 1/4" mount. All I had to do was grind away a bit on the top (of mount) for the 6 1/4 to fit, and that was it.