This is the Kono MS-25 filter paper designed for "2-cup" brewers (01 size Hario) - and in particular the Kono drippers. There are 100 sheets in this pack, and will perfectly fit any 60 degree dripper (V60, Origami, Flower etc).
This is a special, thicker paper, made from Virgin Pulp. It has a rough side on the outside, and smooth (Silky) on the inside, which creates a unique flow rate. It's definitely slower than the Red filter paper, but creates a great clean cup, while still making a vibrant flavour profile, and still a relatively fast brew!
This is an interesting paper, that's definitely worth playing around with - it works great on some heavier natural coffees, with a multiple pour method.