When it comes to teens and safe sex, an ounce of prevention can go a long way.
Anyhow, if the condom feels loose or slips around or it is too big it might be more comfortable and safer to use a slimfit condom. If the condom feels too tight and restrictive it is too small perhaps it would more comfortable and safer to use a larger condom. However, 50% of men can use the standard size condom sold in most stores and passed out at most schools and clinics.
Now I understand this might not be the easiest conversation you have ever had, but you are providing important information that is generally not offered in high school health class.
This first talk should begin to open the dialogue between you. I would suggest circling back. You may even want to consider sending your teen an email as well before the conversation to provide an overview of the most important information you wanted to share. This may give you both a little more space to insure that the information is properly shared and received.
If we can provide further information or support, Lucky Bloke offers a free Condom Concierge Service via email at firstname.lastname@example.org. Our Condom Concierge is trained to offer comprehensive support regarding proper condom sizing, as well as sharing comparative information regarding product specifications and attributes. They are also very happy to support you as you navigate through any condom issues.