The ShockStop Seatpost is 27.2mm in diameter and comes in two different lengths: 350mm and 280mm. Typically, folding bikes use very long seatposts in larger diameters. But, many folding bikes come with and can work with telescopic seatposts. These allow you to use a standard seatpost like the ShockStop by adding an extension that fits into the bike and accepts the standard seatpost. Check with you local bike shop or bike manufacturer to see if one of these is available and if it accepts 27.2mm seatposts. An example of one that accepts 27.2mm seatposts is the Tern telescopic seatpost: