Kefir grains, a symbiotic culture of bacteria and yeasts. Traditional kefir is fermented at ambient temperatures, generally overnight. Fermentation of the lactose yields a sour, carbonated, slightly alcoholic beverage, with a consistency and taste similar to thin yogurt.
Aim: glans expansion. technique: urethral dilatation. I purchased a set of urethral sounds made from surgical quality stainless steel, with the following dimensions: 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38 F (1 F = 3 mm). I have been training for months approximately 1 hour once a week with sounds of successive dimensions and am now able to insert the biggest sound.
1 Imagine trying to insert a sound into the urethra with your subject laying on his stomach. It would be pretty much an impossible endeavor.  Insertion. In order to get that sound in there, you have to make sure the penis is soft. It'll make it easier to allow the sound to slide into the urethra.