I'm translating a text about an antifungal cream sold in aluminum tubes. The plastic cap of each tube has a spike in it used to break the foil/seal in the neck of the tube. 

I'm not sure what these spikes are usually called. I googled but failed to find a description. It is **spike** or some other term?  

[![enter image description here][1]][1]

P.S. Original in Russian:

> 15 г крема в алюминиевой запечатанной тубе с белым полиэтиленовым колпачком, имеющим **перфорационный пробойник**.

> Проколите  запечатывающую мембрану при помощи **острия** на внешней стороне колпачка. 

  [1]: https://i.sstatic.net/rsYL0m.jpg