There are two main types of printed bags; low density & high density. Low density is the "smooth glossy" plastic, often used in retail applications and for trade shows. Both merchandise bags and T-shirt bags are available in low density plastic. High density is the "crinkly or frosted plastic. Merchandise bags and T-shirt bags are available in high density plastic. Grocery store type bags are high density t-shirt bags. These bags are economical and strong.