Replacement Folding Knob, compatible with: E100 (version 1-15)E125 (version 1-15)E150 (version 1-5) Razor Part #W13112099029 Note: Model versions can be determined based on the product ID code on your Razor product. The product ID code can be found on the battery cover and/or on the bottom of the frame. The 7th and 8th numbers in your product ID code are the version number of your Razor product (e.g. "01" = Version 1, "02" = Version 2, etc.).