Very stout hardware. Strong spring. I ordered size 21mm for a heavy stainless steel watch. Shaft diameter 1.9mm. Fully compressed tip-tip length 20mm. Full extended shoulder-shoulder ~23mm.

  The bent pins I took out were installed by a watch / jewelry shop. They were 1.5mm diameter, and shorter in every dimension.

  These pins really improve the feel of the watch band. It feels more crisp and sits straight on my wrist.