MKS Heavy Duty Plastic Servo Output Arms

I was very disappointed when none of these servo arms fitted on my two DS6100 servos. At first I just thought they were going to be a tight fit. But I've tried and tried and they just wont go on. The servos are fitted in a model and removing them will be a pain. Popping on some heavy duty arms should have been straight forward. I am easily able to get a finger firmly under each servo and press the arm on with my thumb, but the splines aren't having any of it. I'm expecting either the arm or the servo case to split, so I've given up.

As advertised. Very good and fast service from Hyper.

Big surprise: I just received 5 horns in one bag! The description should be updated (again?).
The center section is 2.7mm thick, compared to 1.9mm of a standard horn.

Working great. Have them in the wing of my Stream NXT (top drive).

The photo shown is not accurate, the package I received had different content: two arms instead of five, even though even during the confirmation they show the same photo with five arms. When I tried to solve this problem I did not receive an answer.

HyperFlight reply:
MKS changed the contents of the packet, we have now updated the product description. I emailed the customer explaining this, and he replied. He could have returned them for a full refund.