Casement windows with mullions combine side-hinged operation with divided-light styling, but the products available here are mainly casement-window hardware and accessories—not complete mullioned window units. The in-swing egress window is the closest full-window option; the operator and locks are relevant when repairing or securing casement windows. The comparison below clarifies what each item does so you can match it to your project without confusing a replacement part with a complete window.
| Product | Best suited for | Product type |
|---|---|---|
| WINDOW WELL SUPPLY In-Swing Casement Egress Window | Basement replacement or renovation | Complete window |
| N8LokNLok Dual Arm Operator | Specific right-hand operator replacement | Window hardware |
| Prime-Line H 3683 Sash Lock | Older or XOX swing-in casements | Window lock |
| Prime-Line H 3520 Casement Operator | Right-hand square-body crank replacement | Window hardware |
| Prime-Line H 4158 Casement Lock | Casement or awning sash locking | Window lock |
WINDOW WELL SUPPLY In-Swing Egress Window
This 31-by-40-inch in-swing casement egress window is the closest option in this list to a complete window. Its all-vinyl frame is described as maintenance-free, and the window can swing from the left or right. The listing also specifies an 8-inch wall thickness.
Best for: Buyers replacing or adding a basement egress window who need an in-swing casement design. It was selected because it is a window rather than a small replacement part. Limitation: The provided details do not say that it includes decorative mullions or divided-light grilles. Confirm the opening dimensions and project requirements before choosing it.
N8LokNLok Dual Arm Casement Operator
This dual-arm operator is listed as compatible with several wood casement window brands, including Marvin, Bilt Best, Windsor, Vetter, Pozzi, and Shelter. Its long arm measures 10-1/2 inches, and its short arm measures 4-7/16 inches. The listing identifies it as a right-hand part, with handing determined by the hinge side when viewed from outside.
Best for: Repairing a casement window when the existing operator’s handing and arm measurements match. It is included because functional operators are relevant to casement-window renovation, including windows with divided-light styling. Limitation: It is right-hand only; confirm the hinge side and hardware dimensions before ordering.
Prime-Line H 3683 Antique Brass Sash Lock
This diecast-and-steel sash lock is designed for older, butt-hinged casement windows. It is non-handed for right- or left-handed windows. Its surface strike is described for single swing-in casements and can also be used on XOX swing-in windows, where the center panel is fixed and the outer panels are active.
Best for: Buyers replacing a lock on an older or XOX-style swing-in casement. The XOX detail makes it particularly relevant to multi-panel window layouts. Limitation: The listing does not establish that this lock fits every mullioned window; compare the existing lock and strike arrangement first.
Prime-Line H 3520 Square Casement Operator
The H 3520 is a right-hand square-body crank operator, viewed from inside looking out. Its mounting holes are 3-7/8 inches and 4-3/4 inches on center. The arm measures 9 inches from the guide-button center to the crank-operator center when closed.
Best for: Replacing an existing right-hand operator when its mounting-hole spacing and arm measurement match. It was selected as a practical repair component for operating casement sashes. Limitation: The right-hand orientation and specified measurements may not suit other window configurations.
Prime-Line H 4158 Satin Nickel Lock
This single-pack lock is described for casement and awning sashes. Its components use stamped steel and diecast materials. The keeper has a zinc-plated finish, while the housing and lever have a corrosion-resistant satin nickel finish.
Best for: A buyer replacing a casement or awning sash lock who wants a satin nickel finish. The finish and stated window types make it a relevant hardware option for a repair project. Limitation: The provided product details do not specify dimensions or handedness, so compare the existing hardware before selecting it.
Buying Guide: Choosing Casement Windows With Mullions
What do mullions mean on a casement window?
Mullions are vertical or horizontal members that divide a window into sections. In product listings, the term can refer to structural dividers between separate window units or to the appearance of divided panes. Check whether a listing describes actual separate sashes, applied grilles, or simulated divided lights; those terms are not interchangeable.
Are these products complete mullioned windows?
Only the WINDOW WELL SUPPLY product is presented as a complete window, and its listed features do not confirm mullions. The other selections are operators or locks. If you need a new divided-light window, verify the grille style, number of panes, frame material, dimensions, and opening direction directly with the window supplier.
How should I choose replacement hardware?
Match the existing part’s function, handing, dimensions, mounting-hole spacing, and arm geometry. For a lock, compare the latch and keeper layout. For an operator, note the hinge side and measure the arms and mounting points. A similar-looking part may not fit if these details differ.
What should I check before ordering an egress window?
Confirm the rough-opening dimensions, wall depth, swing direction, and local egress requirements with a qualified installer or building official. The listed product measures 31 by 40 inches and specifies an 8-inch wall thickness, but the supplied information does not establish suitability for every basement opening or code requirement.
Frequently Asked Questions
Can I add mullions to an existing casement window?
It depends on the window and the intended look. Ask the manufacturer or a window professional whether compatible grilles are available; do not assume an accessory will fit every sash.
Are mullions and window grilles the same?
Not necessarily. Mullions can divide separate window units, while grilles can create the appearance of divided panes. Check the product description to identify what is included.
Which product here is a complete window?
The WINDOW WELL SUPPLY in-swing casement egress product is listed as a complete window. The other featured products are casement operators or locks.
How do I identify a right-hand casement operator?
Follow the product’s stated viewing position and handing method. For the N8LokNLok operator, determine the hinge side while viewing the window from outside.
Can one casement lock fit every window?
No. Lock style, keeper position, sash design, and dimensions vary. Compare the replacement with the existing hardware before ordering.