Trap extension 1-1/2 inch male x female BSP x 1 inch long.
The standard size for a kitchen sink or bath.
This extends the threaded part of your waste by an additional 1-1/2 inches.
BSP (British Standard Pipe Thread) sizes don’t match up with what you would measure using a ruler. Have a look at the BSPT link at the bottom of this page for more information about how plumbing threads are measured.