For example the price of this part is the same as IWC. Shipping would have been about 4.95 from IWC and 25-30 from FFT. Most parts are price gouged and I personally have had little from them work. The extender I bought I think was 90 and it didn’t move freely on my trigger group, and the charging handle I bought wasn’t long enough and would have torn up my receiver. I did manage a refund on the handle dispite the no refund policy.
I didn’t do my research before purchasing after buying my M4 and ended up unsatisfied with them. This is my experience. Others have their own input.