A rack for supporting a sleds includes a pair of elongated support posts and pairs of elongated support arms that extend from the elongated support posts. Each pair of the elongated support arms defines a sled slot to receive a corresponding sled. To do so, each elongated support arm includes a circuit board guide to receive a chassis-less circuit board substrate of the corresponding sled. The rack may include a cross-member arm associated with each sled slot and an optical connector mounted to each cross-member arm. Additional elongated support posts may be used to provide additional sled slots.