A workholder to hold a workpiece, including a main body partially defining a fluid chamber, and a bladder carried by the main body with an interference fit, further defining the fluid chamber, and composed of an 80 to 100 durometer Shore A scale hardness polymer of a 12:1 to 18:1 diameter-to-wall-thickness ratio. Annular seals may further define the fluid chamber, and are disposed radially between the bladder and main body and axially adjacent the fluid chamber, and are composed of a 60 to 80 durometer Shore A scale hardness polymer. A collet is carried and driven by the bladder for gripping engagement with the workpiece.