Unbacked films 0.2-0.4 mu m thick have been prepared. The films are opaque for He I radiation (21.2 eV) but transmit up to one-third of He II radiation (40.8 eV). Beryllium filters 6 mm across have been mounted inside the tube of a discharge lamp where they can be slid in and out of position. The films were prepared by evaporating beryllium from a tungsten crucible on to a thermoplastic resin substrate at a rate of 10 nm s^-1. Initial vacuum was 4*10^-5 Pa, and 4*10^-4 Pa during evaporation. The plastic was dissolved and the film floated on to a washer.