The range of values varies by era and country, but the focus is on coverage; the values should be sufficient to make up all possible charges using as few stamps as possible. Generally the smallest value will be the smallest unit of currency, or smallest fractional postal rate; for instance, the 1925 regular issue of the United States included a 1⁄2-cent stamp because some rates were expressed in fractions of a cent per ounce. The highest value of the series is generally quite large, typically from 50 to 100 times the normal letter rate; typical values include one pound, five dollars, etc. Not often seen by the average person, they are most common for parcels. The in-between values are usually chosen to "make change" efficiently, for instance 1, 2, 5, 10, 20, 50 in a decimal currency. It is common[citation needed] to include all values between 1 and 10, multiples of 5 from 10 to 50, and multiples of 10 from 50 to 100. Additional "oddball" values may reflect specific common rates, and if the series lasts for a period of time, there may be a number of such unusual values as in the UK QE II Machin series below. Definitives are the workhorse stamps of a country, and as such, they tend to be small, with designs reflecting local culture and history. The definitives of poorer countries will often be very plain and cheaply printed, unlike the large and decorative commemoratives, which are almost pure profit if bought by foreign collectors and never used for postage.