Fit the Piston Seal

Offer the anti-extrusion ring into the seal housing. The ring is of triangular section, the base of the triangle sits on the base of the seal housing.

Offer the seal into the housing above the anti-extrusion ring; insert it into the housing at one side of the piston.

Work around the diameter of the piston, pushing the seal into the housing, until the whole seal has engaged into the housing above the anti-extrusion ring.