go to crutchfield.com and they should tell you the speaker sizes for your vehicle.
6.5" front and rear door speakers
http://www.crutchfield.com/S-96jByR9lvTK/app/car/mycar.aspx ; Front speakers : Dash: 4x6" : Front Door: 6-1/2" ; Far rear speakers : Behind Seat: 4x6"
The two front speakers are 3.5" and the two rear speakers are 6"x9"
3-1/2"
6 1/2 front and rear
The stock speakers in a 1993 Toyota Corolla measure 4 inches in the front and 6 1/2 inches in the rear. The front speakers are located in the dash, and the rear speakers are located in the rear deck.
in the front doors their 6 1/2 in the back for a pickup their 4x10
3-1/4 in front 4 x 10 in back
3-1/4 in front 4 x 10 in back
For a 1998 Dodge Ram 1500 extended cab, there are two different sizes of speakers. The front speakers are 6x9 and the rear are 5-1/4.
The stock front door speakers on 97- 01 lumina are 5.25 round but the depth of the speaker is an important dimension since the speaker is front mounted in an enclosure which is mounted to the door. I replaced my stock speakers with Sony Xplod model XS-R1342. Any 8 ohm model speaker with similar dimensions will work.
Stock speakers should be 4x6's