Bulls X-Ray Colour Gradient Stems – Black and Clear in Short. Stunning colour fusion technology. These stems are ultra durable, sporting a gradual colour change from black to clear. Comes with silver aluminium springs. Also available in Medium and other colours.Bulls X-Ray Colour Gradient Stems – Black and Clear in Medium. Stunning colour fusion technology. These stems are ultra durable, sporting a gradual colour change from black to clear. Comes with silver aluminium springs. Also available in Short and other colours.