If you are seeking for the trading contracts then bitmex remains to be best choice for bitcoin trading. Here you have variety of contract type offers which are paid out using bitcoin. Unlike BitMEX you cannot able to find these contract type varieties in any other sites thus it remains best to provide perpetual contract with high level which do not expires. There are several perpetual available XBT is a speculative bitcoin which has up to multiples of 100 leverages which do not expire and charges low fees. Here people can participate in declines and market rallies with fraction of bitcoin. There is no margin value or liquidation so you can have ups and downs in trading. BitMEX just handle bitcoin alone that is bitcoin profit and loss rather BitMEX do not handle flat currency even when you buy and sell contracts of altcoin. To make the site usage easy you have five navigation keys like trade, account, contracts, references and API.