Modular 12 GA shotgun shells holder

You also need: 4 screw 3x20mm and nuts
Created in onshape: https://cad.onshape.com/documents/143ce3c9dcdc138f2a1fa295/w/ddb69a74b23e12e77c676a4d/e/7163dc1004fbe055dd04c985?renderMode=0&uiState=66f32dd34903c34ebea5325e