Abstract: A transparent needleless injector drug capsule suitable for prefilling with a liquid drug comprises a first inner layer of drug compatible transparent plastics defining a chamber for receiving a liquid drug and a second outer layer of transparent plastics forming a supporting sleeve around the first layer of plastics. Each of the first and second layers of transparent plastics is resistant to discoloration when irradiated by high energy radiation. Thus, a low cost, transparent, needleless injector drug capsule is provided which is capable of being sterilized by high energy irradiation. The capsule may define a body having a main chamber for receiving a liquid drug and for retaining a free piston in a sealing fit for subsequent use in the discharge of a drug, the body also having an extension chamber having an opening for receiving the free piston in a loose fit.