Hi MD, if you have not already watched it, go to the Forum under the spread webinars section and watch the video the Ins and Outs of nadex Spreads series. it does a great job explaining spreads and how the ATM spreads work. Here is the link: Webinar- The In's and Out's of Nadex Spreads
There are multiple spreads you can choose from. Some are at the floor or ceiling, some are priced further away from the current underlying price, some have postive premium, some have negative etc. To most closely mirror the underlying market and there fore move with the market as close to tick per tick / tick per $1, it is best to use the ATm spread, meaning the one where the currently underlying is towards the middle of the spread, not at floor or ceiling. Most of the times your best bet is the wider end of day ATM spread. Hope that helps
