Our TierraCast jumprings are high quality plated brass. nMed Oval- 4x6mm 20g. - Inner Dimensions (ID) are .105 x.166 - 100pcs. per bag We have proudly carried TierraCast for over 25 years! TierraCast products are made in USA with strict compliance of product regulations and a commitment to superior quality in manufacturing, materials and design.