Our Universal T-track features a unique "stacked" T-slot that accepts both 5/16" T-bolts and 1/4" T-bolts, as well as 1/4" Hex-bolts. This means you can use all the hardware and T-track accessories from your old jigs in addition to the newer style hardware. The T-tracks are available in 2 ft, 3 ft, or 4 ft lengths. Mounting screws not included. For added versatility and functionality, combine T-Tracks with 5-1/2"L x 1-1/8"W Hold Down Clamps and 3-1/2"L x 3/4"W Hold Down Clamps. Features: All T-tracks are 3/4" Wide x 3/8" Deep. T-tracks feature pre-drilled mounting holes in base. Holes are 4" on center, 2" from each end. Made of extruded aluminum. Mounting screws not included.