Grade 1 bats can often have blemishes and heartwood, although there is no standard, as others have said. Grade 1+ bats tend to have fewer blemishes and more grains, but interestingly, more heartwood than a regular grade 1 bat. I can see what Matt says about it being a marketing tool, but the grading system is passed down from the willow merchants, so from the very top of the food chain, there is a price differential between the grades, so it's not just the end user who is "fooled into paying more"...