This replacement knob is specifically for any gray trainer manufactured prior to 2007 with a serial number smaller than 50000. This new tension knob features our newer design which is stronger and more durable. We suggest replacing the old knob with our new design.
IMPORTANT: when replacing an old L-bolt with this updated design, you’ll also need a new spring to fit the new bolt diameter. This L-bolt is machine down at one end, but has a larger thread diameter and spring diameter. (Click here to order a new spring).