510k premarket submission is not required when someone is selling an incomplete device to another firm for further completion. If the device is manufactured outside the country and you are importing it, then you don't need 510 premarket submissions if the foreign manufacturer of that device has already submitted it. Read http://demandingbizservices.over-blog.com/2020/07/fda-510-k-submission-a-step-by-step-guide.html

1. FDA 510 k Submission:A Step by Step
Guide
510 k submission is given to FDA to reveal that the device or
product to be marketed should be legalized as it is safe, effective,
and successful. FDA has classified the devices underclass I, II, and
III, which are considered for human use and for the devices which
don't require premarket approval application. Class I devices are
those who are of less risk for the public. This device doesn’t usually
need 510k submission. Devices under class II are those who are of
medium risk and usually premarket clearance by FDA 510 (k)
submission. Classes III devices category are of those are which are
of full risk to the public and must fulfill the requirements, not 510 k
premarket submission. The device's manufacturer should submit a
510 k to FDA; otherwise, the device will be spared from 510 k
premarket requirements of the FDA. Before the marketing of a
device or product,every submitter of 510(k)submission must
receive an approval in written format from the FDA. This approval
means that the device is safe and can be used for commercial
purposes and marketed across the country.

2. 510 k submission guideline
The submitter cannot market its devices until he receives the
approval, which declares that it is substantially equivalent. A
substantial equivalence requires consideration under 510k
submission that they are equal to other legal devices in the market
approved. If FDA doesn't require the devices as substantially
equivalence, then the submitter has to resubmit the other 510k
with all new data. If the FDA approved the device as a substantial
equivalent, it could be marketed across the country. The approval
is made within 90 days by the FDA, as it depends on the details
submitted by the submitter. The product can be marketed instantly
only after the approval by the FDA. 510k submission is required
when a company introduces a new device into a market for the first
time.

4. Requirement for 510 k submission
510 k submission is also required when there is an alteration and
change to a legally marketed device because that alteration or
modifications can impact its safety. 510k premarket submission is
not required when someone is selling an incomplete device to
another firm for further completion. If the device is manufactured
outside the country and you are importing it, then you don't need
510 premarket submissions if the foreign manufacturer of that
device has already submitted it. The categorizing and submission
processes related to medical devices are very different from those
provided for pharma products. That's why it includes that 510k
premarket notification.
Source: http://demandingbizservices.over-blog.com/2020/07/fda-
510-k-submission-a-step-by-step-guide.html