The Quick Curve Ruler and QCR Mini Ruler are designed to be used with Sew Kind of Wonderful patterns. Each ruler has multiple patterns it can be used with. Both rulers have a curve cut-out slot in which a regular 45mm rotary cutter can be used to cut fabric/paper to a specific size or shape as indicated in the patterns.
Quick Curve Ruler patterns have a large citrine/yellow green dot on the front cover and says QCR pattern.
QCR Mini Ruler patterns have a large teal dot on the front cover and say QCR Mini pattern.