Stainless steel water bottles come in a variety of shapes and sizes from bottles that are small enough to fit easily in a pocket or purse, to large models that will hold well over a liter. There are also a number of colors available and some bottles come with graphics lithographed on the outside. Graphics are nice, but consider a neoprene or other sleeve for the bottle since normal use can cause scratches that will mar even the best graphics.

Why are double-walled bottles important? Most bottles are single-walled, which means that they are made from a single layer of stainless steel. Others are double-walled, meaning that they are actually two bottles, one inside the other, that are welded together. Often, the air within the space between these two bottles is drawn out to create a vacuum. That is all a vacuum bottle is, an inner and outer liner, with all of the air sucked out of the empty space between. Vacuum insulation has long been used in bottles designed to carry coffee or soup, and it was natural that this superior insulation system would migrate to bottles designed primarily for drinking water. Vacuum insulation can help keep drinking water cold all day long, which is far superior to what a plastic bottle can do.

Many manufacturers have listened to their customers and begun offering different caps and lids that can be interchanged among many of the different bottles that they make. The advantages of this are obvious: replacement caps are easy to get, and the variety of available caps for every bottle is increased. Caps are usually made of food grade polypropylene, and come in several main styles that most manufacturers provide. The most common is one with a small spout that may be activated by pulling up on a small cap, or by pressing a button. Another common variety is a straight cap, with no sipping ports. This type of cap must be completely removed in order to drink or pour from the bottle.

Another concern when choosing a stainless steel water bottle is the liner. Most of these bottles are medical or food grade stainless steel on the inside with no plastic or epoxy coatings that might touch the beverages inside. A few manufacturers, however, use either a plastic or epoxy coating on the inside of the bottle. This is more common with aluminum bottles, but it does happen with stainless bottles occasionally. If the purpose of the bottle is to avoid the use of plastics and chemicals, then buying a bottle with a plastic coating on the inside makes little sense.