The PRV-U (Russian: Противогаз Ракетных Войск, Улучшенный - "Rocket forces mask, improved"), often erroneously known as the PRWU, is a gas mask used by Soviet missile troops, appearing some time around the 1970s.
The PRVU is a helmet-type gas mask, which stretches completely over the head. The overall shape of the 'face' of the mask is very similar to that of the Soviet PBF and ShMS. The eyepieces, which are not angled as much as those of the GP-5, feature distortion-free lenses and are more suited to soldiers that must aim down an optical sight. It can be found in either grey or black, like most other soviet gas masks of the time.
It accepts Russian and NATO 40mm filters. 
It is based on the ShMS gas mask, the most significant difference between them being that the PRV-U's voice diaphram cover lacks the holes found in the RSh-4 ShMS. The modified cover was designed to protect the voice diaphram from the drops of toxic and caustic rocket fuels and oxidizers (UDMH, triethylamine-xylidine mixtures, nitric acid, nitrogen tetroxide etc.), as the PRV-U was intended for use by missile crews.
Another minor difference between the PRV-U and ShMS is that the metal neck near the filter/tube attachment has a shallow bump, which is meant to serve as an attachment point for a rubber/canvas sleeve that is meant to protect the mask's rubber hose from the dangerous liquids.
The PRV-U kit also includes a specialized bag, which is meant to hold the filter. The bag has two holes punched in the bottom, so that the filter can be placed in the bag and take in air.
- ShMS-R facepiece (Russian: Шлем Маска Специальная, Ракетчик - "Special helmet mask, rocket")
- Rubber hose (as opposed to the canvas hoses used on some other Soviet masks)
- Rubberised hose sleeve
- EO-20P rocket fuel pre-filter
- EO-65K filter