Dumbbell shaped pre-concentrators can be used to facillitate better fluid flow for more efficient sample pre-concentration by minimising flow turbulence. 
 
The pre-concentrator can be customised for different I.D, length, and thread types. The current price is shown for the below mentioned options.
 
Column I.D: 4 mm
Column length: 10 mm
Thread types: 1/4 UNF female