This gripper utilizes toggle arms to open and close the gripper fingers by pulling the center cam pin. The fingers open and close concentrically with about a 1/2" of travel per finger. No fasteners or glue are required for assembly, the pivot pins trap the parts in place. No supports are required if you print the parts as oriented. The cam pin does have some overhangs but caused no problems.

You can find the SLT's files here for download:
https://www.thingiverse.com/thing:266...