What is the difference between 135-gram and 190-gram flannel sheets?

135 gram flannel sheets contain 135 grams of cotton (4.76198 ounces) per square meter of fabric. 190 gram flannel sheets contain 190 grams ( 6.70205 ounces) of cotton per meter of fabric. The more grams per square meter, the heavier ( and usually softer) the sheets will be.