A beautiful solution when you want to mainly pump your penishead and not so much the shaft. The expansion of the shaft of the penis is limited by the smaller inner diameter of the neck of the cylinder. The head on contrary, has much more space for expansion.Lenght of these cylinders are all around 10 inch (25 cm). Available in four different sizes:• Opening 1.75 inch (4.4 cm) / Neck lenght 5.00 inch (12.7 cm) / Inside 3.00 inch (7.6 cm)• Opening 2.00 inch (5.1 cm) / Neck lenght 5.50 inch (14.0 cm) / Inside 3.25 inch (8.3 cm)• Opening 2.25 inch (5.7 cm) / Neck lenght 5.50 inch (14.0 cm) / Inside 3.25 inch (8.3 cm)• Opening 2.50 inch (6.4 cm) / Neck lenght 5.50 inch (14.0 cm) / Inside 3.25 inch (8.3 cm)