First Step" products generally claim over 99% accuracy when used correctly, from the first day of a missed period. Many variations provide rapid results, often within 40 seconds to a few minutes (typically 3 minutes).
They are designed for simple, at-home use with clear result indications: one line for negative and two lines for positive. Some versions, like the "Pen Plus" or "Early Result," can detect pregnancy as early as 7 days after conception or several days before a missed period.