There are two disadvantages of standart plastic pipe coupling devices for people who is blowing cable. One of them is coupling two pipes each other takes too much time and the other one is you can not take out plastic pipe coupling device after cable blowing inside the coupling device. You can take it out only by cutting it means that you can use it only once.
Kosmak is designed and produced steel duct coupling devices to solve these problems.
You will work much more efficient with these tools.