They're replacement blades the Tamiya Modeler’s Knife Pro (item 74098).
• Narrow Chisel blades x5
• 0.55 mm thick.
• Narrower compared to the now available chisel blade (Item 74101, Width: 4mm), and hence may be used in tighter areas.
• suitable for removing protrusion from flat areas of ribs and molds an such like.