Our cups are made from high quality clear acrylic so you can see exactly what's happening in the cup. They are perfect for pairing with an APEX or used by themselves to hang weights. • Perfect for taping or using PervMcSwerve's "water method". • High quality acrylic for durability and longevity. • Clear color for high visibility and easy detection of issues like blisters or edema. HOW TO MEASURE:  • Measure the width of your FLACCID glans to determine which size is appropriate.  • If in-between sizes, sizing down you risk not fitting, sizing up leaves you room to grow.  • If you plan to use the water trick you may be able to use a size up.   • We personally recommend buying multiple sizes just in case and to leave room to grow.  *Vacuum cup pump sold separately* *You do not need a cup pump if you plan on using the water method.*