These have a similar purpose to the shaker in that they are made for session ales, in this case bitters, milds, porters and stouts. There are a couple of key differences. First, they pour a proper pint (and usually have a line indicating where that is on the glass, just to make sure you don’t get ripped off). Second, they have a bit more flourish than the bland shaker. There are basically two variations. The first has a gentle curve covering the upper 2/3 of the glass - Guinness uses these. The second has a straight slope for the bottom two-thirds, and then a bump near the top, flattening out at the mouth of the glass.