Doors 6 3/4 Rear pillars 4x6
usually 6.5 or 6.75 (same mounts, same speakers)
The speakers in a 2006 GMC Sierra 1500 crew cab are 6.5 inches. However, the speaker manufacturer will refer to this size as 6.75 or 6 3/4 inch speakers.
4x6
The 2001 GMC Sierra 1500 dashboard speakers measure 4.5 inches in diameter. The front door speakers measure four inches by six inches. The rear speakers measure five inches by seven inches.
The 2000 Chevrolet 1500 Z 71 front speakers measure three by five inches. The rear speakers measure four by six inches.
5 1/4'' front and rear
In a 2000 chevy Silverado 1500 z71 the front door speakers are 6.5"
6 inches in the front. 6 x 3.5 in the back.
4x6 are the size of the door speakers on 2004 GMC Sierra. Standard cab
There are two pairs of speakers, a pair in the doors and a pair in the rear pillars. The door speakers are 6 1/2". I'm not sure of the rear speaker dimensions, but if you call Crutchfield or look at their site online, you can input your truck details and they will tell you what size the rear ones are.
The 2010 GMC Sierra-1500 has a V6 engine.
The 2011 GMC Sierra-1500 has a V6 engine.