According to Firstrade's website, they trade quotes in increments of 5 cents if the premium is under $3 and 10 cents if the premium is over $3. For VIX that is ridiculous, especially if they don't do price improvement on fills. I have placed VIX orders at $3.34, $1.14 or $0.39 which got filled with TOS. If that is the case, it totally negates the fee advantage of Firstrade. https://help.en-us.firstrade.com/article/173-in-what-price-increments-are-equity-and-index-options-quoted