In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million (ppm, 10−6), parts-per-billion (ppb, 10−9), parts-per-trillion (ppt, 10−12) and parts-per-quadrillion (ppq, 10−15). This notation is not part of the International System of Units (SI) system and its meaning is ambiguous.

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  1. RobMa

    Jerks at Midwest Gun Works supplies refunded my money on an order I made several days ago.

    Not one word, no email. The money was just deposited back into my account. I legally purchased the items (non-serialized ) several days ago so they could've shipped it to me at no risk regardless of whether the ban gets signed tomorrow or not. Even if there is an injunction levied against this...
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