Universal Brew Group Spray Nozzle 30mm, with a M10x1 thread.
Used with most E61 grouphead machines like Bezzera, BFC, Bianchi, Brasilia, ECM, ECM Manufacture, Expobar, Faema, Fiamma, Fiorenzato CS, Futura, Gaggia Spagna, Grimac, Italcrem, Mairali, Pavoni, Promac, Reneka, Royal, Sab Italia, Sanremo, Scala, VFA Expres, Vibiemme, Visacrem and Wega.
Universal Brew Group Spray Nozzle 30mm is found right under your screen filter.
You need to remove this one in order to get acces to the nozzle.
Use as flat as possible wrench or other tool, so not to break the part and thus, the water flow afterwards.