This sealing plug is used to fill non-populated spots in the 1999-2007 Hayabusa and early GSXR ECU connectors to keep moisture, dirt and debris out.  Also used on MoTeC M84, MoTeC M400, MoTeC M800, Link, ViPec V44 and ViPec V88 ECU connectors.  These small white plugs were once considered unobtainable, but here they are!  

Sold in packs of 5, 10 and 25.