A step up, in terms of performance, from the card guides are the Calmark Retainers and Birtcher PCB Tainers. Within this category, Birtcher’s products are called PCB Tainers and Calmark’s products are called retainers. These products look different, but both provide the necessary spring pressure to insure retention of the PCB to the sheet metal enclosure. While these products provide more retention than a card guide, they too should only be used for lower shock and vibration environments. Birtcher’s PCB Tainers, including the 15-20 series which have the same profile but different board thicknesses and the 21 model that features a narrow profile, all feature a flared opening for easy card insertion and come in a choice of three materials and six finishes. Although not shown here, the 35 and 37 series have slightly different shape and profile but function similarly. Calmark’s line up of retainers include the 125/126 which are stainless steel, or the 165 and 166 which are alloy 10 beryllium copper. The coined edges allow smooth insertion and extraction without damage to the card and spring fingers hold the card against the rigid side providing dampening under shock and vibration. Independent sections on the rigid side maximize contact with printed circuit card. All of these products are electrically conductive and ideal for applications with low heat dissipation, and are well suited for any low shock or vibration application such as test and measurement or automation and control applications.