Kustoms are modified cars from the 1950s and early 1960s done in the customizing styles of that time period.

The usage of a "K" for "Kustom" rather than a "C", is said to have originated from car builder George Barris (although it is not confirmed). This style generally consists of, but it not limited to starting with a 2-door coupe. Lowering the suspension. Chopping down the roof line,(usually chopped more in the rear to give a "raked back" look, B-pillars are also commonly leaned to enhance this look). Sectioning and/or channeling the body, (removing a section from the center of the body). Certain pieces of Side trim is usually removed or "shaved" to make the car look longer, lower and smoother. Often times bits and pieces of trim from other model cars, are cut, spliced and added to give the car a totally new and interesting "line" to lead the eye in the direction that the Kustomizer wishes it to go. Door handles are also "shaved" as well, electric solenoids or cables are installed. Buttons are installed in hidden locations and used to open the doors. Trunk lids and other pieces of the body can also be altered in this matter. The head and tail lights of a true Kustom may or may not be the original ones manufactured with the car. Some popular swaps would be putting Oldsmobile or Buick headlights in another model for example. Headlights, tail lights, antenna(e) are also subject to term and act called "Frenching", Where the object is cut from the body, a "box" in the shape of the item is fabricated and welded into the original hole. The part is then installed back into the "Frenching Pocket" giving it a look of being recessed into the body. Traditionally, "Lead", (a mixture of 70% lead, and 30% tin) is used in bodywork of the area instead of modern polyester fillers or fiberglass, after the metal shaping is done to prepare for paint. "Leading" connotes a true Kustom "Lead Sled", which was started in the '50s to imply a large, slow lead-filled car that was all flash and could not hold its own at the races. This was sometimes not the case however and certain Kustoms packed some serious punch under the hood. Today, however calling someone's car a "Lead Sled" will generally be taken as a compliment.

Grills are often changed on lead sleds as well. Some owners use pieces of other grills to Kustomize their own. For example, using a DeSoto grill in a '50 Mercury, or a LaSalle (Cadillac) grill in a '36 Ford, two of the most recognized and classic combinations of all time. "Flipper" style hubcaps are popular on Kustoms, such as '57 Dodge Lancer (4 bars) , '56 Oldsmobile Fiesta (3 bars) , '59 Dodge lancer or "Crabs" as they are said to resemble a crab, Other such as '57 and '49 Cadillac Hubcaps are also acceptable and referred to as "Sombreros", '57 Plymouth "cones", etc. There were also other popular styles that were purely after market and never came factory stock on another car, like "Hollywood" flippers, or "Crossbars" for example. It is an up-spoken rule of sorts that a Kustom will have white wall tires, most authentic being bias ply style tires. The width of the whitewall denotes the era that the particular car hearkens to. For example, a Kustom built in a '40s style will typically have true "wide Whites" which are 3 inches or more in width, where the white rubber extends behind the rim of the wheel, this style is period correct for Kustoms up to the mid '50s. From the mid to late '50s, a narrower (but still wide) extending to the rim of the wheel. In 1956, GM had a concept car called "Biscayne" (styling elements that were later used on Corvettes, '57 Chevrolets, and Corvairs.) This car featured some new height tech looking tires that had only a very thin stripe of whitewall rubber. By 1958, Cadillac starts selling cars with these type of "Skinny Whites" or "Inch walls" they were an instant hit and all the rage with the Kustom Krowd. This style of thinner 1 in, 1.5 in, 1.3 in, 3/8 in, or 5/8 in whitewall continued to be popular into the '60s and are still common on some newer cars today. "Lakes pipes" were another Kustom main stay, long or short chrome pipes that run back from behind the front wheels wells. The have either one of three removable end plugs for running flat through with open exhaust. Side pipes are similar but do not include removable plugs, "Bellflower" tips are similar but run from the rear wheel well back under the bumper, a style that emerged in the Bellflower, Ca. area in the early '60s.

This school of Kustomizing is called building a "Stock Component Kustom" where parts from other makes and years are used to alter the appearance of the car. The term "mild Kustom" refers to a fairly conservative approach to Kustomizing, where the majority of the original beauty and identity of the car are retained. A "Full Kustom" refers to a car that has been severely altered from every aspect possible almost every exterior panel is re-shaped , interiors, dash, engine bay, suspension, heavily chromed mechanical components, etc. There is also a third version of a true Kustom, the "Bomb". These were the original Lowriders, which developed back in the '40s though the '60s alongside the other types of "Kustoms" These usually were similar to the mild Kustoms in that they emphasize keeping the car as original as possible, but using custom paint, chrome, and often covered with every type of bolt-on period correct accessory possible. Each addition accessory on a Bomb is like having one more little badge of honor. Bomb usually have heavily altered suspensions that incorporate traditional hydraulics setups, (the most authentic use discarded WWII aircraft hydraulic components, which were largely available after the war.) Some Use of "Air Bags" are used these days on all genera of Kustoms the suspension height, not traditional but often given a "free pass" in this day and age.

These cars can also be referred to as custom cars, leadsleds or sleds. The term kustom is generally used as a signifier that the car was done in the '50s and early '60s style as opposed to later more modern styles.