High quality artists' grade colored pencils made by Sanford/USA.
Their smooth, wax based leads allow intense colors and smooth blendings. Because of their outstanding characteristics, they are favored by many artists and designers.
Prismacolor Premier colored pencils are sold in a range of 150 colors and a colorless (not pigmented) pencil "colorless Blender".
Years ago, the british company Berol sold these pencils under the trademark
Karismacolor. They looked a little different (the pencils were coated colorless and beveled at one end), but the leads were identical to the Prismacolor Premier.