The ImmEdge™ Pen (H-4000) is an improvement over the PAP pen for immunohistochemistry, immunocytochemistry, immunofluorescence, and in situ hybridization. It is designed to provide a heat-stable, water-repellent barrier that keeps reagents localized on tissue specimens and prevents mixing of reagents when multiple sections are mounted on the same slide. The ImmEdge™ Pen barrier is stable for use buffers with and without detergent (e.g. Tween 20 or Triton X-100, etc.).