Does anybody know if an actual trade is required to trigger a stop? I'm wondering specifically about some of the illiquid/low volume contracts. For example, if I have a stop sell order at a price of 50.00, and the contract goes offered at 50.00, and keeps getting offered lower before finally trading down at 49.00. Does this just contribute to slippage? Or will a offer at/lower than a stop sell price trigger the stop?