Is the fill or show rule good for 10 or 20 contracts? I've seen both. In the link below, he says 20: http://www.optionsuniversity.com/blog/options-universitys-options-101-part-52/ Many thanks for any input.
I'm not sure what they're talking about. Each option exchange in the US, if you route your order to them through direct market access (DMA) has to either fill your order or show it, even 1 lots. When I was a market maker on the amex we had to show 10 up markets. That was a long time ago. Now, MM can be show one lots. If you use a "smart router", I'm not sure where your order goes or how it's handled. But, the exchanges must show your order if it's within the markets.
I think in the article the OP linked to, the "20 contracts" refers to the minimum required for an All-or-None order. But the minimum varies. I think IB's is 10, for example. Fill-or-Show should not be subject to any minimum. That is, even 1 contract should be shown if it is not bought by the MM.
With respect to Fill-or-Show, SmartRouting gives a kind of preview show to hidden institutional order flow. After that preview the order would be subject to the "fill or show" rule.