Before ordering, read the product description. Previous reviews indicate many did not see "Compact" in the product description. Compact means Small. It's not another synonym for portability. For the standard, large brush, search for the Standard brush head.
Sample compact brush head came with my Sonicare 2pack brush kit (2 std, 1 compact). When I got around to using it, I found it excellent for reaching the back teeth. My hygienist scolds me for not keeping the back teeth clean but it's not easy to do with the standard size heads unless one has more space. Oral B brushes are the right size for me and Colgate are too large if that helps readers get an idea. Can't find the compact version in stores easily so Amazon is a great resource. The subscription plan was to save money but since it took a while to process online, I accidentally ended up with a double order. So if you subscribe, wait a day before trying again.
Recyling tip: a hammer knocks off the super strong magnets when the brush head is ready for trash. Knock off in a box because once it goes flying, it's difficult to locate. Box walls will rebound the sucker so you can pick up the loose item. Keep away from children (tendency to swallow which results in nasty hospital bill) and any credit cards or stuff easily demagnetized. Makes for great magnet crafts.

I have owned my Sonicare product for three years and love it. I decided to try the compact head replacement brushes and love them. They see mto do a better job cleaning all of the areas better than the standard brushes.

These are refills for our electric toothbrush. We like the Sonicare product. This is our second Sonicare toothbrush.

I was disappointed in the size of the replacement head. It was not clearly stated in add that it was a smaller version of the original toothbrush head.

The small head size is just perfect for people with a strong gag reflex. Brushes teeth clean just as well as the standard head.