The best advice I can give you regarding feeding a young, small dragon staple insects that have either a shell or an exoskeleton, such as crickets or roaches (Besides that if they are larger than the space between his eyes then they are too big for him to eat, which is a good rule to follow), is that IF YOU HAVE ANY DOUBT THAT THE CRICKET OR OTHER INSECT YOU ARE ABOUT TO FEED YOUR DRAGON MIGHT BE TOO BIG, ANY DOUBT AT ALL, THEN DON'T FEED IT TO HIM. PERIOD.
There was a young Dragon that a new member posted an urgent question about a few months ago in the "Beardie ER", I believe he was 2 or 3 months old, that they had fed a cricket that they weren't sure about, but figured he could handle it, and he swallowed it with a bit of trouble but then was fine, and the next day the Dragon died, probably of a bowel obstruction or because the cricket never made it out of his esophagus, stomach, or intestines. That's what you have to realize, that even if your Dragon manages to swallow a larger size of cricket, that doesn't mean he's okay, as it's not only his mouth and throat that are small, but also his stomach, intestines, etc. that are also very small, and if he eats an insect with a hard shell or exoskeleton and he cannot fully digest it because it's too large, and big, hard pieces of the insect have to travel through their GI Tract all the way out of the other end, a lot of the time this causes Bowel ruptures and internal bleeding, tearing, etc.
So while you should never, ever feed him a cricket, roach, or any other insect that has a shell or hard exoskeleton that is larger than the space between his eyes, if you're in a situation like your current one where you're just not sure, then your rule needs to be IF YOU EVEN QUESTION THE SIZE OF AN INSECT, THEN DON'T FEED IT TO HIM. You're a lot better off feeding him a higher number of crickets that you know are small and not an issue than you are feeding him fewer crickets that are larger, but that you're worrying about.
Also realize that depending on WHERE you buy your crickets from, they are going to be sized differently. Some places use "Small, Medium, Large", some use the "Number Scale" method, etc. And even the places/vendors who use the same size labels are not going to ship you the same size of crickets..For example, if you're buying medium crickets at Petco and they're all DEFINITELY smaller than the space between your Dragon's eyes, without a doubt they are fine, and then you order 500 size medium crickets from an online vendor to save money, don't be surprised if the online vendor's size medium crickets are larger or smaller than Petco's size mediums are.
Since the medium size crickets that you bought and have currently have caused you enough doubt and worry that you've posted a question on the forum about them, then that tells me that they are just simply too large to feed your Dragon, and you're best to get rid of them. This is not something that you want to "Chance" or just say "He'll probably be okay with this one", as it only takes one cricket that's too large to cause a tragedy.
This is another reason why I have always fed BSFL as my main staple insect, they are completely soft-bodied, and even young, small baby Dragons can eat the size larges.
