It looks like you're asking about a 1/4" olive fitting. Here are some details about this type of fitting:

• Material: Typically made of brass or copper, which offers durability and corrosion resistance
• Connections: Designed to fit 1/4" tubing, often used in compression fittings
• Applications: Commonly used in plumbing, gas, and hydraulic systems to create a secure, leak-free connection
• Pressure and Temperature Ratings: These fittings usually have a pressure rating up to 400 psi and can withstand temperatures ranging from -65°F to 250°F