Air Lift Fittings 21732 Air Lift Company has developed dependable air spring suspension products since our inception in 1949. All our efforts are spent ensuring your safety and comfort by designing, engineering and manufacturing the highest quality suspension products. BUSHINGS-1/2IN. MNPT X 3/8IN. FNPT Bushings; 1/2 in. MNPT x 3/8 in. FNPT; Air Lift Bushings- 1/2in Mnpt X 3/8in Fnpt