After Selecting your base, Choose what wheels you will be using with your system. 6x70, SCI (3 hole) and Forever Sharp (5 Hole) are all options. The SCI adapter comes with included bolts to install the wheel. If buying the Forever Sharp wheel adapter you use the Stock bolts that come with your wheel with this adapter. If you need them they are M6x40mm Bolts. The 6x70 adapter comes with no bolts due to varying need depending on the many variations of 6x70 wheels out there. Price is determined by how much material is used to make the item.