Yes, the RC-21B and RC-21BR can be used on a confocal microscope.

In general, one critical consideration when using imaging and recording chambers in confocal imaging is the small working distance of the objective. All Warner chambers use a #1 coverslip as the chamber floor which should allow visualization of the sample within the chamber with immersion objectives.

It should be noticed, however, that some smaller chambers (such as the RC-21) have a smaller opening on the bottom of the platform. Therefore, one should verify that your specific objective can be brought into close apposition with the chamber bottom.

Finally, you should consider using the RC-30 for confocal imaging needs. This chamber has been specifically designed for this purpose.