Take the ester off testosterone and what remains is testosterone base - the raw hormone, suspended in water rather than dissolved in oil. That is exactly what Testobase is: Alpha Pharma's aqueous suspension, ten ampoules at 100 mg/ml.
With no ester to be cleaved there is no delay and no depot, so the hormone becomes available almost at once and is gone again quickly. Suspensions are the shortest-acting testosterone preparations there are. They are also microcrystalline, which means the ampoule needs shaking before it is drawn and the injection is known to be less comfortable than an oil.
