First let's check what type of seat you currently have. If you look on the backside of the seat, you will find a gold colored sticker with technical information. Here you'll find a serial number. If this number contains a B, you have the broad seat. If this number contains an S you have the small seat. If your chair has the wider B model, then we can exchange it for the smaller model. If you have the S version (small), we do not have a smaller seat, but perhaps a different model would be a good solution for a better fit for you (suggestion: ErgoSolex).