Quilt cotton fabric... Fat Quarters  - 100% cotton.  
Based on regular weight cotton: 1 yard is 6 oz. First Class, 2 yards is 12 oz. First Class. The priority flat rate envelope holds up to 4 yards. The flat rate bubble envelope holds up to 8 yards. The medium flat rate box holds up to 23 yards. The large flat rate box holds up to 32-33 yards.
 
Some computer monitors display colors differently and the exact color may not be what is shown on your screen. Red, orange and turquoise is very hard to photograph.