Bolt-in seat rails for the VW Golf Mk4 (1999–2005) allow you to mount aftermarket bucket or sport seats directly to the factory floor mounting points without welding or custom fabrication. 
They act as a vehicle-specific adapter, providing a safe, secure base to attach your universal seat sliders and side mounts.

While the floor-side bolts to the VW, the upper surface features a multi-slot design that accepts sliders and side mounts from most brands

The base bracket bolts directly into the factory threaded holes and OEM rail lips. Aftermarket sliding rails can then bolted to the bracket, followed by L brackets or the seat itself. 

To pass LVVTA Cert the Belt Buckle mount will need to removed and mounted to the trans tunnel