When it comes to drinks on the rocks, most fall into either the category of highball or lowball. The main difference is that a highball is in a tall glass, and a lowball is in a short glass. The glasses come in different styles, but that’s basically what you need to know.
However, some things have changed, and many bars now serve classic highball drinks as lowballs. Examples include the Screwdriver, the Cape Codder, the Gin and Tonic, the Rum and Coke, and the list goes on. Even though you might think you’re getting less, if the bartender is making the drink right, you’re not getting less alcohol; you’re getting less mixer.
Most bartenders use and most recipes call for the same amount of liquor in these drinks whether they’re made with tall or short (the amount usually being 1 1/2 or 2 ounces). Therefore, the amount of mixer that goes into the drink is what changes. So yes, you are getting less if you get one of these in a lowball glass, but your drink will actually be stronger. If you still want the larger drink, simply ask for it tall.
On this site, when you see a drink on the rocks that ends with you filling up the glass with a mixer, you’re usually free to make that in either a short or tall glass. Some exceptions apply (most dairy drinks on the rocks are always short), but know that you have some room in selecting your glassware.