The nozzle is attached to the P120C full-scale model solid rocket motor for Ariane 6 and Vega-C.
The P120C is the largest solid-propellant motor ever built in one segment, at almost 11.5 m long and about 3.4 m in diameter. Two or four will be strapped to Ariane 6 as boosters for liftoff.
Vega-C is expected to debut in mid-2019 with P120C as the first-stage motor, which will increase performance from Vega’s current 1.5 t to about 2.2 t in a reference 700 km polar orbit.
http://www.esa.int/spaceinimages/Images/2018/02/P120C_gains_a_nozzle
