Contact Shimano directly and they'll probably send you a metal version, they do the UN54 with both, I believe they were made for different markets (although I've always had a random plastic or metal one included when ordering online).
The plastic ones are better in my opinion (as long as they don't snap)... the metal cups are more difficult to remove/install and creak from time to time in my experience.
Contact Shimano directly and they'll probably send you a metal version, they do the UN54 with both, I believe they were made for different markets (although I've always had a random plastic or metal one included when ordering online).
The plastic ones are better in my opinion (as long as they don't snap)... the metal cups are more difficult to remove/install and creak from time to time in my experience.