Encyclopedia
Penetration
Penetration: a consistency indicator expressed as the distance in tenths of a millimeter to which a standard needle vertically penetrates a material sample under specified load, temperature, and loading time
Source: Order of Rosavtodor dated 20 October 2008 No. 436-r
"On the Issuance and Application of ODМ 218.7.002-2008 'Recommendations on the Method for Determining the Depth of Penetration of a Needle for Viscous Petroleum Road Bitumens'"