All pieces are randomly picked by our team. Yes! we will give you big pieces, 5 lbs – biggest piece is about 5-6 inches ( about 3 lbs) 20 lbs (BEST DEAL!)- biggest piece is about 7-11 inches (about 7-9 lbs) We always try to fill big pieces in the package first then fill the rest with medium and small sized pieces, so you have some big rocks as dominant element for your layout. Other sellers usually give you all same sized rocks (medium and small, easy to ship) The more you buy, the easier for our team to pick out larger and better stone for you. The 5 and 10 lbs Small Rock are small pieces, size from 1 to 3 inches, mainly use for substrate for shrimp, snail and little fish. Safe and great looking rock for your tank This rock will not alter the water values Shipping Detail: All items will be shipped within 1 working day after receive the payment, (except for weekend) Fast shipping with USPS priority mail 2-3 days About Feedback: If you are not satisfied with the item, please contact us by eBay messenger center before you leave negative feedback, we will solve the problem within 1 working day. Thanks for your understanding.