I took a chance and bought this for a '77 Exciter 440. Since no dimensions are given I figured I'd buy it and hope it would fit. Well the 3" bolt spacing was correct. The '76-'77 Exciters with the Keihin round slide need a little smaller boot than this one. I believe this boot is made for the '78 and up Exciters with the butterfly carb. I was able to clamp it down enough to get a good seal on mine so I'm running it.
My old intake flange was cracked and dryed out causing a air leak. When I priced the part with yamaha, the part was $46 plus shipping. So for $10 through dennis kirk and i had it in 2-days as well as a good fit, this was a great buy.