I found the numbers of the K & N Filters for Speedmasters & Americas: RC2900. I modified my Air Box by cutting off the Tubes from the Box to the Throttle Bodies & then used the K & Ns. This way I still had the mounts my Side Cover and can use the original Air Filter hole for tools or what have you. The sound and power difference is outstanding!!! The Air Box is a PAIN to take out, but now that I've made the modification I wish I'd done it sooner!!!