Remove your current watch strap by proper spring bar tool.
Use masking tape to protect your watch before installing new watch strap.
Use the 'fork end' of the spring bar tool, depress the spring bar, so it slides inside the watch lug.
Repeat on another side.
And then hold the two strap ends firmly and pull them apart, make sure the watch strap is securely installed.
The spring bar of speed pin type watch strap is different with normal one. It's fixed with watch strap.
Simply insert one end of the spring bar into the lug. When the spring bar has been pushed down, use a free finger to push the top of the endlink out gently.
Repeat on the other side. Finished.