Cryptocurrencies are usually characterized by wild price swings and extreme volatility. But there is one cryptocurrency that is designed to be the exact opposite.

Stablecoins, as the name suggests, are intended to be stable in price. That is, they are supposed to hold roughly the same value from the day you buy one to the day you spend it or trade it in. That’s because, unlike other cryptocurrencies, the price of most stablecoins are benchmarked to a fiat currency, such as the US dollar, or a commodity like gold, although many stablecoins today are pegged to the dollar.

So investors buy stablecoins not to make a profit but instead as a place to store money within the cryptocurrency infrastructure and to use when buying and selling other crypto assets. They also are used for other types of financial exchanges, such as lending and borrowing or sending payments overseas — for example, to family members — in a much faster, more seamless way than through other means. “They’re a medium of exchange,” said Stephen McKeon, an associate professor of finance at the University of Oregon and a partner at a crypto-focused investment fund that he says now settles more than half its transactions using stablecoin.

The amount of stablecoins available has grown quickly in the past year. As of October 20, the combined supply of stablecoins from the ten biggest issuers was $127.8 billion, according to data from The Block, a provider of crypto research and analysis. That’s up from $21.6 billion just a year earlier. The supply from the largest issuer, Tether, jumped from $16.3 billion to $72.6 billion in the same period, an increase of 345%. The second biggest issuer, Circle, grew its supply even faster — from $2.8 billion to $32.4 billion, an increase of more than 1,000%.