Custom orthotics are ones that are "custom to your feet". In other words you have been given orthotics that are specifically designed for your feet.
There are good and bad reasons in going down the custom orthotic route. Here are just a few:
1- "Off-the shelf" orthotics can be picked up by anybody. Sometimes one size does not fit all and sometimes certain problems can cause certain conditions to appear within the feet. If those conditions are not sorted out first then any orthotic will not work.
2- Custom orthotics can only be prescribed by a clinician. This is good in that they should be able to deem treatment options necessary to your condition. I.e...do you really need them and if you do, what are these orthotics going to be like? Check out the do I really need custom orthotics? page to see what I mean.
3- Unfortunately many clinicians think they can prescribe orthotics which means that one orthotic from one source can be very different from another...
4- Quality of the orthotic depends on if the clinician sends your template off to a company who specializes in orthotics (but even these can vary in quality) or if the clinician does it themselves. Either way if the clinician or company decides to save money the quality of the orthotics reduce meaning that they can disintegrate quicker than you would have liked. Always check for samples.
5- Insurance companies will demand that only certain clinicians will be authorized to create your custom orthotic. This basically states that the insurance companies do not trust a lot of the clinician types out there and also that you haven't picked up some from a store somewhere.
6- Orthotics are expensive, ranging from $200- 500 a go. Do you have any fall back- if they hurt are you going to get them altered for free? If they break are you going to get them replaced? In other words, what is your guarantee?
7- I must reiterate- do you really need them? Do you need a certain type for your work or recreation? A sports person needs a completely different set than to a postal worker who needs a different, more durable style but would need them replaced more.
8- Most clinicians fail to realize that if you put any type of orthotic into your shoe, you will reduce the depth of the shoe. You may have to get new foot wear to accommodate the new orthotic. Be careful that some clinicians will up-sell you a shoe...check around first to see if you can buy a similar one for for a lot less- remember as well that some insurance companies will not cover this.
Custom orthotics are meant to be designed for you to sort out a clinical problem.
Companies that sell "over the counter" orthotics will not allow you to ask them for custom orthotics because they usually need a template/ cast and a prescription outlining what you need. Only a qualified clinician can make the judgement.