From time to time, we have some blackout fabric that isn't quite perfect in appearance - it is perfectly usable, but may have some small marks so we can't sell it as 'first' stock. We think it would be a shame to throw it away so we offer it at a discounted price. It is a bargain really, because when your blackout is up, you can't see it anyway!
The only difference is that there may be some small marks on the fabric (and these are often on the reverse).
All of our seconds blackout blinds and fabrics are listed on the 'Bargains' page - availability can change daily, and these do tend to be very popular, so it is worth checking regularly if you are looking for something in particular.