Pressure relief valve, 1/8" BSP (M) - 100 bar approx. opening pressure. When mounted to the pump body, prevents damage in the system caused by over pressure produced by thermal expansion (1 °C increase in temperature can cause up to 10 bar increase in the system pressure). Opens at approx. 100 bar. Possibility to connect either a 1/4" hose with a clamp or a hose with 1/8" BSP (F) fitting as oil return live.