In efforts to prevent centralization of mining cryptonight coins by ASICs manufactures, Monero developers implemented some changes to its hashing algorithm. This made existing Criptonight ASICs unable to mine Monero (XMR) and other cryptonight based coins. The changes may not be noticeable by non-ASIC miners, but will be large enough to prevent CryptoNight ASICs from mining Monero. If new ASICs that adapt to the change are manufactured, they will only work until the next hash modification, which will be after every 6 months.
Individuals that want to engage in mining the coin will have to use CryptoNightV7, which is a new Proof-of-work algorithm forked by monero as a counter measure to wave of Cryptonight ASIC miners being manufactured.
It is anticipated that more cryptonight coins will follow suit also fork to the new CryptoNightV7 mining algorithm and thus increase the demand rate of the CryptoNightV7 Mining Rigs algorithm.
Currently, there are not a lot of mining rigs available for the CryptoNightV7. It is, however, anticipated that more will be availed in the future. There are a few miners in the market who support the new V7 of the hashing algorithm such as Cast XMR version 0.9.2.
It is unclear whether other cryptonight coins will follow the forking route, though it is highly likely. Miners should therefore be keen on any news regarding the coins in case they fork.