A weizen glass is tall and narrow at the base, then flares into a soft bulb near the rim. Every part of that outline is doing a job. Bavarian wheat beer is among the most carbonated styles brewed, and it throws a dense, meringue-like head that a straight-sided glass simply cannot hold. The bulb gives the foam somewhere to sit instead of over the edge of your glass, and because the aromatics of a Hefeweizen live in that head, keeping it intact is what keeps the banana and clove esters arriving at your nose sip after sip.The narrow, tapered base is usually explained as a sediment trap, holding the yeast at the bottom rather than letting it slide into your mouth. Treat that as received wisdom rather than physics, but the tall column does have a real effect you can see: it shows off the haze and the rising bubbles, which is much of the pleasure of the style.Half a litre is the standard, and it is not arbitrary. German wheat beer comes in 50cl bottles, and a weizen glass is sized so bottle plus foam fits in a single unhurried pour. Rinse the glass with cold water first so the foam has something to cling to, pour at a steep angle down the side, then straighten up and let the last third build the head. If the beer is bottle-conditioned, roll the bottle gently before opening to rouse the yeast.Suits: Hefeweizen, Dunkelweizen, Kristallweizen, Weizenbock, American wheat, and at a push a Gose.