DZUS FASTENERS
https://files.southco.com/static/Literature/D4.en.pdf#Quarter-Turn-Fasteners-D4-H3
D4 - DZUS® Standard-Line Quarter-Turn Fasteners. Designed for quick-access, the DZUS® D4 Quarter-Turn Fastener provides accurate, secure engagement and vibration resistance for demanding applications across industries. Southco offers a wide range of DZUS® D4 Fasteners that provide enhanced functionality in addition to Aerospace grade D4 Quarter-Turn Fasteners that meet Aerospace certification requirements. ( CONTENT COURTESY- SOUTHCO.COM)