A billet separator with an 11.1 mm bore, matched to AN4 hose. AN4 turns up everywhere on a build: turbo oil feeds, gauge and sender lines, clutch and brake plumbing, and small fuel returns. Where two of those lines share a route, this separator holds them at a fixed spacing so they stay parallel through the run and cannot saw against one another as the engine moves on its mounts. It also gives you a convenient point to anchor the pair to a bracket or bulkhead. Do the fitting with the lines already routed and the engine at rest, and nip the fastener up firmly without over-clamping a PTFE-lined hose.