Fotodiox Pro 柔光箱，通用型速度環與轉接板，適用於3-6吋直徑無卡口閃光燈 - 標準柔光箱用7.75吋速度環板

I was worried about compatibility with my older softbox, but the 6-inch outer diameter fits perfectly and the all-metal construction feels solid. No wobble or cheap plastic parts here.

For the price, this all-metal speedring feels solid, and the 6-inch insert locks into my softbox without any wobble. I was worried about compatibility, but it connected to my strobe's speedring plate on the first try.

The metal insert fits perfectly into my standard softbox and feels solid enough to hold even a heavy strobe without any wobble. I was relieved to find the 6-inch outer diameter matched my modifier exactly.