The Suzuki Bandit 400 (confirmed by @Phil), RF400, and perhaps the 250 also, use a rectangular shaped "o-ring" in the top of the slide housing. Part number is 13278-21E00. As usual, it is not shown in parts books except for the RF400. This part seems to be extinct. However, if I can get the dimensions from a Yamaha slide housing (Zeal or 3LN6/7) then I will be able to determine the amount of stretch that is applied to the part. From there I need the dimensions of the Suzuki slide housing groove and I can then calculate the correct size for the extinct Suzuki part. Please help. In this image you can see how much larger the Suzuki part is than the Yamaha Zeal version.