Concealed (built in) showers with a variable height rail (also known as a BIV shower) have a wall outlet fitting which the shower hose attaches to.
When replacing the wall outlet, our recommendation is to replace like-for-like if possible to ensure a suitable fit to the pipework and to maintain the original look of your shower.
You may want to identify your shower first, for help with this see our article Need help identifying your Shower or Part?
Once you have found your shower, you can navigate it's spare parts to find the correct wall outlet.
It might be easier to match your outlet visually!
Browse all of our wall outlets here
Tip: If the parts aren't shown under the shower's spare parts, bare in mind that sometimes the outlet is listed within the rail kit's spare parts (try navigating to the showers head holder or hose and finding the compatible rail set/fittings spares listing!)
Some information on cross-compatibility: Wall outlets have a half inch BSP thread on the end the hose fits to - this is fairly standard across most showers. You'll notice that some outlets fit to the pipework in a different way, for example compression fit, a screw thread or a specific mounting pack, so you may want to check how yours currently fits if looking to replace with a different wall outlet fitting.