We offer Lightspeed Trader (4 Legs), Sterling Trader Pro (4 Legs) , Realtick (8 Legs) and CBOE Silexx (8 Legs). To get the 8 legs you have to direct your orders to exchanges that accept that like CBOE but not our SMART route. Cboe, C2, ISE, EDGX, MIAX, and ELMD all take 8.
To my knowledge (as Robert said) the maximum (for US equity options) was 8 legs. But indeed I see 16 if I look on the internet:
https://cdn.cboe.com/resources/rele...roduces-16-Leg-Maximum-for-Complex-Orders.pdf