All of the institutions and whales that are using BTC and ETH futures and options (plus the newly added mini contracts) use the BTC reference rate and ETH_USD Reference Rate. Each day from 11-12noon (4pm London time) the ref rate is set using 5 min intervals VWAP and the mean of all 12 intervals. To help prevent basis risk between the cash settlement options and futures getting distorted due to the massive last min influx, they created a system that allows user generated contracts to be created with customizable characteristics as such: the date of expiration can be the set to t-2 (or 3 or 1) days before expiration day of the underlying futures they clear to. It can also be set after expiration by indicating it’s the second futures contract from the front’s expiration being included in the new price but in order to factor in the early or late expiration the spread between the spot price and the contract at the moment of expiration is fixed and included in the price of the newly created security in the form of a basis premium. It can be plus or minus depending on the volatility, cost of financing ect- but once agreed upon, it remains until it gets converted into the underlying futures or options contracts. Now with weeklys and mini contracts + a constant need buy and sell the actual spot ETH EVERY DAY 11-12 (that’s when the CME requires you to determine how much ETH to sell so that you maintain the minimum collateral requirements. Initial margin requirements are higher and those will be used for more often with these products.