Bars are made from pure .999 silver and come in a varity of sizes, shapes and designs generally come in 1oz, 5oz, 10, 100oz, 1000oz bars but come in other sizes as well. There are many known and unknown mints that produce odd weight bars usually stamping the exact weight on the bar. Most common mints are Englehard, Johnson Mathey, Sunshine, U.S. assay. North west territorial mint, Pan America, OPM, NTR, RMC, Apmex. Sivertowne, Scottsdale Silver, and others but all are very tradable and make great investment.