This Profoto Glass Cover -300K for theB1, B1X, D1, and D2 Monolights lowers (warms) the color temperature of the light emitted by 300K. It approximates the use of an 81A filter on a camera lens. Use it if the color temperature is too blue for your preference or assignment requirements. The dome also diffuses the output of the flash while widening the beam spread. It snaps into place over the flashtube assembly.