In Borderlands 3 there is a broad range of uses for the rare element, and therefore players will want to keep an eye on the best spots to farm it. In short, players can purchase cosmetic items or weapons with Eridium. Clarification: The third slot-machine is the third one from the entrance. The first right around the corner. Check the boards directly above the 3 slot rolls, the prizes are displayed there.
Slot machines are found in Moxxi's Den in Sanctuary, The Holy Spirits just outside Outlook, and in an abandoned house with two vendors outside in The Dust. By using them, cash will be taken from you and the three reels will spin. This cost scales upwards as the player progresses the main quest. Depending on what they stop on, you may be rewarded.
Borderlands 3 Slot Machine Guide
Slot cost is determined by the formula: 1.12^L * 48, where L is the items level, you may be rolling for items below or above your actual character level.
Lining up 3 of a kind gives you special rewards:

- 7 — gives you a customization item.
- Bandit Head — drops a grenade that deals massive damage in a large area, so get out of there fast! The machine will play a sound clip of someone saying 'Boom time!' and the grenade will beep much like a Suicide Psycho's grenade does.
- Single Eridium Bar — will give you 4 Eridium.
- Stack of 2 Eridium Bars — will give you 8 Eridium.
- Stack of 3 Eridium Bars — will give you 12 Eridium and complete the 'Jackpot!' challenge.
- Borderlands Logo — will give you an orange weapon of your level and complete the 'Jackpot!' challenge.
- Markus Head — will give you a purple weapon of your level.
- Leg — will give you a blue weapon of your level.
- Cherry — will give you a green weapon of your level.
- Bell — will give you a large amount of cash.
Borderlands 3 Slot Machine Broken Machine
Other combinations containing the same symbol in the first two positions will give either a white weapon of your level (if the third symbol is a bandit head) or cash (if the third symbol is a bell or the first two are bells and the third anything other than a bandit head).

Borderlands 3 Slot Machine Broken Hand
If there are no matches at all, or if symbols other than the first two match (i.e. A-B-A or B-A-A) a three note sound will play and no reward will be received.