A gold-colored metal window lock mechanism with an offset espag, positioned against a plain background.
Technical drawing of a metal strip with two mounting holes spaced 43mm apart, showing dimensions including 8mm thickness, 16mm width, and a customizable length and backset (20mm or 25mm).
Diagram showing two types of UPVC window gearboxes: Offset Gearbox on the left and Inline Gearbox on the right, with red window profiles and labeled parts for comparison.
A gold-colored metal window lock mechanism with an offset espag, positioned against a plain background.
Technical drawing of a metal strip with two mounting holes spaced 43mm apart, showing dimensions including 8mm thickness, 16mm width, and a customizable length and backset (20mm or 25mm).
Diagram showing two types of UPVC window gearboxes: Offset Gearbox on the left and Inline Gearbox on the right, with red window profiles and labeled parts for comparison.
Avocet

UPVC Window Lock - Offset Espag - 400mm – Replacement uPVC Window PartUPVC Window Lock - Offset Espag - 400mm

£7.49 SKU: HS2663
Backset
Backset
Order by 2pm for same-day dispatch
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Same-day dispatch on orders before 2pm

This is the mechanism inside the window frame that is operated by the handle Gearbox is positioned over to one side on the rail (offset) Important Measurements

1) Overall length

2) The 'Backset' (20mm, 25mm)

4) Rail Width (Usually 16mm)

Key benefits
  • Offse espag mechanism - fits older offset-pattern windows
  • 250mm to 800mm lengthst - match your window height
  • Direct replacement - fits most older uPVC windows
Product overview

This is the mechanism inside the window frame that is operated by the handle

Gearbox is positioned over to one side on the rail (offset)

Important Measurements

1) Overall length

2) The 'Backset' (20mm, 25mm)

4) Rail Width (Usually 16mm)
Delivery & Returns

How much is delivery?

UK Mainland Delivery is £2.99 on all items no matter how many you order!

Northern Ireland, Scottish Highlands, Channel Islands £6.00.

We do not offer International Delivery (Ireland, France, Spain etc).

When will my order be dispatched?

Orders before 3pm (Monday to Friday) are usually dispatched same day but may take up to 24 hours.

When will I receive my item?

We ship on 2 working day courier. Fully Tracked. Tracking will be emailed on dispatch. 

Special order items such as keyed alike locks will take longer to dispatch. Please refer to product description for lead times. 

I haven't received my item?

Please email us your name, order number and date of purchase.

We prefer email as it allows us time to research and respond.

Returns Information

We operate a 30 day refunds and return policy. 

If you change your mind you must return the product back to us within 30 days of delivery

Please include a copy of your invoice and a note stating reason for return. 

Additional keys, locks keyed alike or built to code are non refundable as they are personalised made to order goods.

Any refund, which is due to a fault or other defect, will include a refund of the applicable delivery charges otherwise not. 

It is the buyers responsibility to arrange the return of goods to us. We do not offer a collection service for returning items. 

Items must be returned including original product packaging and accessories.

We reserve the right to refuse any returns that do not comply with this policy.

Please post returns to the following address:

Home Secure (Online)

Unit 5, Brookfield Drive

Liverpool, L9 7AJ

United Kingdom

Frequently Asked Questions

A 400mm offset espag window lock is a multipoint locking mechanism designed for uPVC windows with an off-centre handle spindle position. It helps secure the window by engaging locking points along the frame.

The 400mm measurement indicates the overall length of the espag mechanism. Matching this size with your existing lock is important for proper fit and smooth operation.

Signs of a failing espag include difficulty turning the handle, poor locking performance, stiffness, or the window not closing securely.

No, compatibility depends on the spindle position, backset, and dimensions of your current mechanism. Always compare specifications before ordering a replacement.

Choosing the correct mechanism depends on your window type, size, and locking configuration. To learn more, read: How to Choose the Right Window Mechanism: Friction Stays & Espagnolette