The BSK12 Brain Slice Keeper has been designed to pre-incubate a large number of brain slices prior to transfer into recording chambers or for the incubation of preparations in experimental test media. This keeper consists of twelve closely fitting acrylic ‘C’ rings that fit into their own through-hole, located in a circular manifold. Removable netting is wedged between the ‘C’ ring and it’s hole. In operation, the twelve rings located on a manifold with netting are totally immersed in an ACSF-filled purpose designed holding vessel into which a 95% O2, 5% CO2 gas mixture is supplied through an airstone bubbler. The bubbler is located in a central tube chamber connected to the upper manifold. The bubbles rising from the base saturate the ACSF and provide constant circulation of medium to the slices which rest on the nylon nets. Bubbles are restricted to rising in the central chamber and are prevented from being trapped under the slices, thereby ensuring a continuous circulation of medium. Slices remain viable for many hours in these conditions. The BSK12 together with the holding vessel can be easily placed into a water bath for regulating the incubating temperature as desired. A lid with a conical profile ensures that condensation drops do not fall directly above the slices. When in place, the fluid level is maintained at least 3mm above the ’C’ rings. This ensures circulation of fluid over the top and downwards towards the slices. The typical fluid volume with BSK12 is 500ml but can be reduced by adding large glass spheres into the base.