The center bar buckle is one of the most common and universal buckles. Center bar buckles do not require a keeper, the back side of the buckle serves that purpose. They are normally used in lighter weight applications such as light garment leather, vinyl, nylon, etc. Although on some occasions we have successfully used them with some heavier leathers as well. For most heavy leather applications we recommend our roller buckles instead. "Glide Bar" buckles use a "fake" roller. There is no actual moving roller on this tyle of buckle. This differs from a "true roller" center bar buckle . On those buckles there is a real rolling buckle. The difference is expense vs. the need for a true roller. If used in heavier materials the true roller does allow the material to more easily glide through the buckle. Available in the sizes shown in the chart below. Here's some additional information:
What's all this about heel bar buckles, center bar buckles, cart buckles and such? | 
