EDIT: Prop Stops are now available here: http://www.fpvmanuals.com/prop-stop
fpvmanuals is currently creating laser cut prop stops for folding props that prevent the prop halves to bend too far in or out. There is a version of this available for sale in europe made by aero-naut:
and it looks like this:
While this piece is only 2 Euros each, the shipping is a whopping $21 to the US and took over 4 weeks for my order. So for 2 of these, you'll spend over $26 and wait four weeks... not good.
Our new fpvmanuals version will be sold in a pair of two for front and back. They will be made out of black Delrin.
Fpvmanuals will sell the pair of these with free shipping (to anywhere in the US) for $9 USD. Payments will be accepted with PayPal.
We will only make a small test run of about 20 of these pairs to see if this is something worth producing/selling. If you're interested in buying a pair, respond here and you will be first on the list to receive a PM when they are ready, which will be in about 10 days. The kit will include one prop stop that is 40mm wide and the other will be 45mm wide. They can be sanded down to exact size for your prop mount and prop halves. Your prop mount should be 40mm or less in width.