Clip in hair extension, it's the most popular hair extension in the world now, it's very easy for you to attached the hair extension to your head, the detailed information about clip in hair extension as the following: 

1 clip on one piece, the width is 1.5" 
2 clips on one piece, the width is 4.0" 
3 clips on one piece, the wdith is 6.0" 
3 clips on one piece, the wdith is 8.0" 
4 clips on one piece, the width is 8.0" 

The above information is for single piece, they can also be arranged in full set, such as 8 pcs full set <2*8.0" +2*6.0"+2*4.0"+2*1.5> and so on.