This specific variant of Autumn humbucker pickup is traditional Soapbar P90 sizing (roughly 85.6mm x 35.1mm cover for example) and you can choose whether to have them as body mount, or pickguard mount. Body mount is the traditional way soapbar P90s are mounted, with wood screws going through the pickup cover and into the guitars pickup cavity with either foam or springs underneath for height adjustment.
If you need the pickup to suspect from a pickguard, you will need to select pickguard mount. The pickup will be made with small tabs either side of the cover, allowing suspended mounting to a pickguard/ring via screws and springs.
If you are at all unsure which spec you need, please get in touch with me with some info on your guitar, photos etc and I will help guide you in which you'll need for that guitar to ensure correct fitment - james@homeoftone.co.uk