Please note NEO & NEO Plus series use different accessories.
This NEO Series accessory helps connect the Plastic Hot Water Bidet Hose to your bidet. The 3/8" size is included with your original NEO 320 bidet kit. The 1/2" size is an alternative, larger sizing for use with non-standard supply valves.
3/8" T-Adapter: You have a standard North American supply valve size of 3/8".
1/2" T-Adapter: You have a 1/2" hot water supply valve — a common size used for plumbing outside of North America and RV toilets.