This part is a Double 3/4" Barb Adapter x 1" Street.
The Glue Side glues inside a 1" Fitting (like a coupler) and the other side would accept (2) 3/4" vinyl tubing that would measure...
Barb Adapter 3/4" Barb x 1/2" Spigot , The Glue Side glues inside a 1/2" Fitting which would measure 3/4" and a 3/4" ID tube would be glued over the barb.
This part is a 3/4" Barb Adapter x 3/4" Slip / 1" Street.
The Glue Side glues inside a 1" Fitting (like a coupler) and the inside would accept a 3/4" Pipe flex or hard that would measure...
This part is a (1) 3/4" X 1" Barbed Coupler that fits 1" OD , 3/4" ID Clear Hose on one side and 1 1/4" OD , 1" ID on the other side.
These are used for connecting Clear Hoses together in Hot Tubs...