Deribit has pledged to launch on Tuesday a service that allows clients to trade combinations, that is two related options trades in one order, and waive fees for part of certain combinations.

Deribit, which trades futures and options on the main cryptocurrencies, plans to launch on August 23 functionality to trade combinations or “combos” for the first time, effectively enabling traders to execute two trades in a single order.

The crypto market, which has seen Ethereum options open interest spike in the past month, said it will waive fees on the second leg of a combo where the second trade is in the opposite direction, so the fee on a sell is scratched following an initial buy, for example.

Deribit will group together buy and sell trades made by a client and waive the fees on the lowest group, the firm said in a client circular.

If the buys and sells match perfectly, Deribit will waive the group with the lower fees.  The waiver could cut client fees by up to 50% where the trader is posting a balance of buy and sell orders.

The introduction of combos comes as the cryptocurrency market is reporting ether options open interest at over 4 million lots, which is a record and up from just over 1 million contracts a year ago.

The record open interest is linked to the Ethereum merge in September, which has in recent weeks boosted trading volumes and open positions in options and futures linked to the cryptocurrency.

Deribit went live in May with options on Solana, meaning the cryptocurrency derivatives market now offers futures and options on three of the most popular digital currencies.

CME Group said last week it will start trading Ethereum options next month, marking the latest step in the Chicago group’s cryptocurrency roll-out and reflecting the success of CME’s ether future.