The adapter is the metallic device that holds the booster and fuse and fastens them in the shell. The adapter, therefore, is a broad ring, screw-threaded both outside and inside. The inside diameter is uniform, so as to allow the same size of booster and fuse to be screwed into shell of different sizes. The outside diameters of the adapters vary with the sizes of the shell they are made to fit, the rings thus being thicker or thinner as the case may require. Fuses of several sorts are employed by the modern artillerist; and with shell equipped with adapters, any fuse may be inserted in the field right at the gun. Unexpectedly the manufacture of boosters and adapters proved to be much more difficult than it appeared to be at the start, and the shortage of these devices was a limiting factor in the American production of shell. On May 1, 1917, drawings and specifications were sent to the principal manufacturers of ammunition and ammunition components inviting bids on 3-inch ammunition. These bids were opened on May 15, 1917, and after full discussion with the Council of National Defense orders were placed for 9,000,000 rounds of 3-inch shell and shrapnel ammunition. The bids for shell and shrapnel ammunition for all the other calibers of guns and howitzers we had on hand then were about to be asked, when the French mission to this country arrived; and the sending out of proposals was deferred, while discussion ensued as to changing our 3-inch and 6-inch artillery to 75-millimeter and 155-millimeter calibers, so as to make our ammunition interchangeable with that of the French. This decision was made June 5, 1917. There then took place much discussion and consideration of the French ammunition. The French had several distinct types of shell, ranging from the very thin walled high capacity kind to the thicker walled types. The French specifications were radically different from our own or those of the British. The steel shell in the French practice was subjected to a drastic heat treatment, which did not seem necessary to us for the thicker walled types of shell. The French fusing system also was entirely different from that used by our service. French fuses were carried separately, and the adapter and the booster casing were screwed permanently into the shell. Our decision to adopt French types of ammunition made it necessary to rearrange all our plans, and to obtain drawings of the shell, boosters, adapters, and fuses from France. This caused much negotiating, and a considerable amount of time was consumed in getting the necessary specifications and drawings here.