While the basic contour of Coca-Cola bottles has remained, it has been refined several times for various reasons. The first was a practical one. The first contour bottles were wider in their middle section than they are now, and were not very steady on conveyor belts. They had to be made thinner to prevent tipping, but most people think the appearance is also more balanced and attractive. When the plastic 20-ounce bottles were introduced for use in vending machines, slight variations in design were required. Also, large sized bottles such as two- and three-liter family size bottles of Coca-Cola, could not carry the same signature contoured look on technical grounds. Is gift selection difficult for you for certain "hard-to-buy-for" friends and relatives? One possibility is adding to their collection of some kind of memorabilia, or even getting them started on a collection with some specific theme. Many people enjoy Coke, and like getting and collecting various articles with the familiar red logo. Best of all, Coca-Cola collectibles come in every price range and nearly every type of item. The company produces many seasonal and special items throughout the year. Many of the items, which range from clothing to coasters, are collectible.