You can get them without the silicone waterproofing tube, or remove it if you have ones that came with that. Ideally they should be stuck to a material such as

You can get them without the silicone waterproofing tube, or remove it if you have ones that came with that. Ideally they should be stuck to a material such as metal that can help with conductive heat dissipation - especially if you get the kind with extra-bright "5050" LEDs rather than the standard "3528" components. However I don't think that is absolutely necessary - and I have also never heard of any kind of warnings against using them indoors, whether waterproof or not.