The Lamy Studio Fountain pen has a unique propeller style clip that has a slight twist. The cap snaps on and off and also posts with a "click". 

Product Specifications
Length: 5.5 in.(139.7mm)
Posted Length: 6.0 in.(152.4mm)
Diameter: 0.5 in.(12.7mm)
Weight: 1.2 oz.(34.02g)