A set of metal door lock mechanisms, including cases and gearboxes, typically used in multipoint door locks.
Diagram showing gearbox measurement with labels for Backset (A) – distance from lock strip edge to center of keyhole, and PZ (B) – distance from center of keyhole to center of spindle.
A set of metal door lock mechanisms, including cases and gearboxes, typically used in multipoint door locks.
Diagram showing gearbox measurement with labels for Backset (A) – distance from lock strip edge to center of keyhole, and PZ (B) – distance from center of keyhole to center of spindle.
Fullex

Fullex SL16 Gearbox – Replacement Centre Case for uPVC Multipoint Door Lock – 35mm/45mm/55mm Backset 68mm PZFullex SL16 Gearbox - 35mm/45mm/55mm Backset - 68mm PZ

£49.99 SKU: HS3262
Backset
Backset
Order by 2pm for same-day dispatch
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Same-day dispatch on orders before 2pm

The gearbox is the most common part to fail on a Fullex multipoint lock — replace just this centre case, not the full strip, and save.Check your backset is 35mm/45mm/55mm before ordering.

Key benefits
  • Direct Fullex replacement - matches the model in your door
  • Restores multipoint lock function - saves replacing the full strip
  • Check the model on your existing case - before ordering they vary
Product overview

Fullex SL16 Replacement Gearbox

The Fullex SL16 centre case gearbox is the mechanism inside your uPVC door that is operated by the handle. It is the part most likely to fail when a multipoint door lock stops working.

Replacing just the gearbox is far more cost effective than buying a complete new lock. The centre case re-attaches to your existing locking strip.

Key Measurements

The most important measurements are the Backset (35mm, 45mm or 55mm) and 68mm PZ.

This gearbox is non-handed, fitting both left and right-handed doors.
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

The Fullex SL16 gearbox is the core component of a multipoint locking system. It controls the handle and key operation, ensuring all locking points engage securely along the door.

Common signs include a stiff or loose handle, difficulty turning the key, or the door not locking properly. These issues often indicate internal wear and should be addressed early.

No, compatibility depends on measurements such as backset, PZ centres, and the specific lock design. Always match your existing gearbox specifications before purchasing.

Yes, in many cases the centre case gearbox can be replaced on its own, making it a cost-effective way to restore your door’s functionality.

Regular checks can help prevent sudden lock failure and avoid getting locked in or out. Learn more in Check This Before Your Next Let-In: Is the Door Gearbox Still Fit for Purpose.