I have seen and previously used oil based before, also, though not near as efficient this is the only type of test I would use transdermally, I never tried it, but did think about it. Would have to adjust for only 20-25% absorption, but this was the cheapest form of test I saw as far as raws went, and I was sick of pinning other things constantly, but just went for long estered test instead. At the time I think it would have cost about .50 day in terms of raws cost to get the equivalent of about a 50-75mgs of pinned test base, theoritically of course. Also would have to add in the cost of carrier, etc.