Please see the links below for the blades that will fit your model FS400:
https://www.lsengineers.co.uk/catalog/product/view/id/22769 - Blade
https://www.lsengineers.co.uk/catalog/product/view/id/10182 - non gen Blade
https://www.lsengineers.co.uk/catalog/product/view/id/162458 - Fixing Kit
Please, mind that only logged in users can submit questions