Isinglass, powder, 'Drifine'.
A traditional proteinaceous fining agent derived from fish swim bladders and used mostly with whites and sparkling wines, but will also remove harsh tannins in reds.
Unlike gelatin it needs no counterfining with tannin or keiselsol. Drifine is a pre-hydrolyzed form of isinglass which requires only 30 minutes hydration, at or near 60°F (16°C), instead of the typical 2 to 6 days for standard isinglass; nor does it need pH adjustment.
Normal usage is 0.01 to 0.1 gram per gallon.