He¡¯s talking about the older stuff that was laid out on a 2.54mm (1/10¡±) grid.? DIP packages are that size, as are most headers.? Of course there are 1.27mm headers (1/20¡±) as well.
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Most newer stuff is metric, like the 2mm headers, your 4mm headers, as well as most SMD stuff.? Or mixed, like 2x7mm LEDs with 1/10¡± spaced leads.
