Clear polycarbonate Y Reducer. Choice of 1/2" to dual 3/8", or 3/8" to dual 1/4". INSIDE DIAMETER IS FULL SIZE FOR NON-RESTRICTIVE FLOW! For example - a 1/2" barb has 1/2" ID and thin wall, so the tubing fits easily. These are perfect for splitting flow from a 1/2" pump to dual 3/8" water blocks. The 3/8" to 1/4 reducer will work great for running dual Black Ice Micro radiators in a 3/8" cooling loop!