Medical device assembly

A medical device for use with a fluid storage container comprising:

• a hub including a sidewall having an inside surface defining a cavity, an open proximal end, and a distal end having an opening therethrough in fluid communication with the cavity;
• a first indicating element having a distal end attached to the distal end of the hub and a free proximal end extending into the cavity, the first indicating element forming a peripheral recess with the sidewall of the hub;
• and
• a second indicating element disposed in the cavity of the hub including an open proximal end, an open distal end and a body extending from the open proximal end of the second indicating element to the open distal end of the second indicating element, the body having an inside surface of the body defining a hollow interior for enveloping the first indicating element to permit the body to enter the recess upon application of a distally directed force on the second indicating element, the inside surface of the body defining a first diameter region, a second diameter region and a third diameter region, the second diameter region has a diameter that is greater than a diameter of the first diameter region and a diameter that is smaller than a diameter of the third diameter region, wherein the first diameter region forms an entrance angle at the distal end of the second indicating element to permit the second indicating element to move distally over the first indicating element, wherein the entrance angle, the first diameter region, the second diameter region and the third diameter region create line contact between the second indicating element and the first indicating element throughout a range of distal movement of the first diameter region and the second diameter region distally past the first indicating element.