21SLKK08MPX Plug with hose nut and spring guard

Frequently Asked Questions about Quick Connect Couplings & Plugs

• Is it called a quick coupling or a quick release coupling?

  Both terms can be used and mean exactly the same thing. We use the faster, shorter term: quick coupling.

• What is the common standard compressed air coupling used everywhere on compressors?

  This is usually a standard series 26 compressed air coupling made of brass with a nominal diameter of 7.2. Depending on the required sealing material and connection thread or connection hose, several products can be considered: Standard quick couplings

• What does single shut-off or double shut-off mean?

  In single shut-off connection systems, a valve is only installed in the quick coupling, which prevents the medium from escaping after disconnection. In double shut-off connections, the plug also contains a valve that prevents leakage. Attention: The quick coupling and plug must be compatible with each other. A quick coupling designed for double shut-off (item number containing KB) also requires a plug (item number containing SB) capable of this.

• Can I combine a shut-off quick coupling with a non-shut-off plug?

  If the quick coupling is a single shut-off variant, it is possible to couple it with a straight-through plug. However, a plug designed for double shut-off also requires a shut-off quick coupling to be connected.

• How do I find the right plug for my quick coupling?

  For quick couplings and plugs, you will find a list of all matching counterparts at the bottom of each page.

• Which seal do I need in the quick coupling for hydraulic oil/steam/gasoline?

  Depending on the medium, a different sealing material is required in the quick coupling. The medium may attack the seal, causing it to swell or become brittle, which can lead to leaks over time. A list of which sealing material is suitable for which medium can be found here: O-ring resistance chart

• What does "two-hand operation" mean?

  With two-hand operation, the quick coupling and plug can only be connected if the sleeve on the quick coupling is pulled back during the coupling process.

• When do I need a pressure eliminator?

  The pressure eliminator allows trouble-free coupling even under accumulated or residual pressure. A miniature valve automatically relieves the pressure in the connecting element during coupling. However, this generally only works if one side is depressurized. The component with the pressure eliminator must be installed on the pressurized side.

• What does "dead-space-free" mean?

  In so-called dead-space-free connections, there is no volume between the quick coupling and plug that escapes upon disconnection. The entire medium remains behind the shut-off valves on both the quick coupling and plug sides. This means there is no spillage of residual fluid that is typically trapped between the two valves in standard connections. These low-leakage quick couplings contain "KL" in their item number.

• Can quick couplings be made mistake-proof against mix-ups?

  To prevent lines from being swapped when changing connections on a control panel, for example, you can use coded quick couplings and plugs. The coding is both color-based and mechanical (different shapes), making an incorrect connection impossible. View coded quick couplings

General Questions

• When do I have to provide a VAT ID number?

  If you are a customer from another EU country, please enter your VAT ID number when registering. This prevents you from being charged German value-added tax (VAT). Delivery to other EU countries is tax-free upon successful verification of your VAT ID number. Customers outside the EU must not enter any other tax number in the VAT ID field, as this will lead to a registration error. This includes, for example, the UK, USA, Canada, Switzerland, etc. Customers from Germany will always be charged German VAT. Entering your VAT ID number is therefore optional and does not change anything.

• Which countries do you deliver to?

  Customers from various European countries, as well as North America and a few other nations, can order directly in the online shop. A current, complete list can be found here: Shipping Information

• We are a university/college/school/authority and can only purchase on account. Is this possible with you?

  Yes, if our system recognizes from your entered contact details that you belong to this group, you will automatically be given this payment option to choose from. If purchase on account is not displayed, please send us an email to shop@maku-industrie.de with your contact details and we will manually grant your user account authorization to purchase on account.

• What is the delivery time?

  Within Germany, delivery usually takes 1-2 business days via UPS. This transit time is already factored into the delivery time stated for our items.

• Why can't I order via Express even though the products are in stock?

  Usually, this problem occurs when "prepayment" is selected as the payment method. Change the payment method to one where payment is processed immediately upon completing the order, such as PayPal, credit card, Amazon Pay, etc. After that, an Express shipping option should also be available.