This is a 19mm binder and key. It fits many vintage style frames with brazed seat lugs. 19mm is maybe the most common size. You will need to measure your seat lug and buy a bolt that is just a little shorter than what you need so it can compress that clamp. A 19mm binder has an effective clamping reach of about 15 - 25mm. Note that this type binder has a key on one side so that it doesn't rotate while fastening. Make sure your seat lug has a key slot. The "key" and other dimensions are detailed in the technical drawing among this listings images.
 
Key Features: 
  • Size: 19mm
  • Key Type: Penta Pin 
  • Material: Stainless Steel 316
  • Qty: 1 x 19mm Binder, 1 x L-Key
$9.00 X