This is the Bottle Pressure Regulator Assembly used for the Dr. Oligo 48. There are 3 of these on one instrument. It comes with all of the fittings including the over pressure valve.  
This is an exchange part which means that the original defective part must be returned to Biolytic within 2 weeks of receiving this exchange part. If you do not want an exchange part but you need a new part please order part number: 606-106023. 
The defective part you are returning must have only normal wear or damage. Rusted or smasher parts or items that are missing things are not acceptable as returnable for credit on an exchange part.