want to build my own power supply with pot ajustments

http://www.ebay.com/itm/Low-Ripple-LM2596-DC-DC-Converter-Step-Down-Power-Module-In-4-40V-Out-1-5-35V-/170799546371?pt=LH_DefaultDomain_0&hash=item27c4724003
this is the one that i posted earlier it has some good photos to read the chip and caps.. but this listing does not have much info... like the one that was removed
sorry hopefully this link will work

below i found this one but it dose not say what they use but i think the ratings are what i need again it says 94% efficiency but i dont know what regulator they used but its probably cheaper then buy this one with all the spare parts i have around sorry about all the mix up and thank you for looking in to this again ... let me know if this is the switching non liner one that would be good for useing as a adjustable regulator for a home made power supply

http://www.ebay.com/itm/DC-DC-Buck-Step-Down-Converter-8-40V-to-3-30V-8A-Switching-Power-Supply-Module-/140717698442?pt=LH_DefaultDomain_0&hash=item20c36dad8a

as long as you think this is going to work