There are two types of brush head: Snap/Click-on and Twist/Screw-on. Below you will find details on the differences between these two types of brush heads.

• The snap-on or click-on brush heads are compatible with most of our rechargeable Sonicare Toothbrush handles. These will fit all Philips Sonicare toothbrush handles except for the PowerUp Battery and Essence models.
• The twist-on or screw-on brush heads are our original and standard brush heads and are compatible with the old models of toothbrushes. 

You can refer to our Sonicare brush head advisor page  choose which brush head is right for your toothbrush handle.

You can identify the Smart brush heads by the Smart icon at the base of the brush head as shown in the image below.
A microchip in the Philips Sonicare Smart brush head tells your DiamondClean Smart which brush head you are using. So if you click on a gum-care brush head, for example, your toothbrush knows to select the optimal mode and intensity for that brush head.