Bulls Spine Dart Shafts – Polycarbonate with Aluminium Top – Yellow – Tweenie. These coloured dart stems all come with a black aluminium top which creates a strong grip to the flight. The colour variations of the shaft give a vibrant look to your set up. Available in 3 sizes.Bulls Spine Dart Shafts – Polycarbonate with Aluminium Top – Yellow – Medium. These coloured dart stems all come with a black aluminium top which creates a strong grip to the flight. The colour variations of the shaft give a vibrant look to your set up. Available in 3 sizes.Bulls Spine Dart Shafts – Polycarbonate with Aluminium Top – Yellow – Short. These coloured dart stems all come with a black aluminium top which creates a strong grip to the flight. The colour variations of the shaft give a vibrant look to your set up. Available in 3 sizes.