JMP Chrome Fork Tube FORKTUBE_JMP_7730812. 1x Chrome JMP Fork Tube. Product Type: Fork Tube. Outer Diameter : 43 mm. Inner Diameter : 39.4 mm. Connection Top : No thread. Bottom Connection : External Thread. Thread : 43 x 1.0. You can send us a message by using the “Questions and answers” section towards the bottom of the page.