Online Store › Roll of .315 Flat Spline - 1000ft. Image 1 of 1 Roll of .315 Flat Spline - 1000ft. $40.99 Roll of .315 Flat Spline. 1000ft. Great for installing 18/14 and 20/20 in new aluminum extrusions. Quantity: Add To Cart Added! Roll of .315 Flat Spline. 1000ft. Great for installing 18/14 and 20/20 in new aluminum extrusions.