Ah, so here's a little twist. I emailed foster and smith just to make sure of compatibility before I ordered.
Thank you for your e-mail. We apologize, as we currently do not carry bulkhead fitting pieces specifically designed for use with 1/4" RO
tubing. As the fittings you have mentioned are for use with flexible airline tubing, it may not be possible to properly fit and secure RO
tubes. If you are able to obtain a threaded RO
adapter, it may however be possible to install a plastic nut and gasket to create a bulkhead for your source water reservoir. These pieces should be available at most local hardware or plumbing supply stores.