Product Details
Color Details
Size DetailsFrequently Asked Questions
Are the Saint Laurent SL M40 sunglasses prescription-ready?
What face shapes work best with the SL M40 square frames?
What are the measurements of the Saint Laurent SL M40?
What is the Monogram collection and what makes it special?
Do these sunglasses provide UV protection?
Are Saint Laurent sunglasses made from sustainable materials?
Compare With Similar Frames
How the Saint Laurent Monogram SL M40 Sunglasses stacks up against the closest alternatives we carry.
- Higher bridge fit (16mm vs 18mm) better suited for those who need more nose clearance
- Slightly larger lens width (55mm vs 54mm) for more coverage
- Longer temples (145mm vs 140mm) for better fit on larger heads
- More affordable price point ($181 vs $302)
- Similar square shape and acetate construction
- Classic collection offers timeless design without logo branding
- Same Monogram collection with YSL Cassandre logo on temples
- Similar premium acetate construction and quality
- Alternative shape option within the same collection
Read the full comparison
Saint Laurent SL M40 vs SL M40/F vs SL 174: Which Frame is Right for You?
Choosing between Saint Laurent's square frames comes down to fit, budget, and how much you value the Monogram collection's signature details.
SL M40 vs SL M40/F: Standard Fit or Asian Fit?
The SL M40/F is the Asian Fit version of our SL M40, designed with a higher bridge (16mm vs 18mm) and longer temples (145mm vs 140mm). If you find that most sunglasses sit too low on your nose or the temples feel tight behind your ears, the M40/F's adjusted proportions will provide better clearance and comfort. The 55mm lens width also offers slightly more coverage than the standard 54mm.
Both share the same Monogram collection DNA—premium recycled acetate frames with the gold-tone YSL Cassandre logo on the temples. The choice is purely about fit, not style or quality.
SL M40 vs SL 174: Monogram vs Classic Collection
The SL 174 from the Classic collection offers a similar square acetate silhouette at a significantly lower price ($181 vs $302). Both are prescription-ready and feature quality Italian construction, but the SL 174 takes a more understated approach without the signature YSL logo hardware on the temples.
Choose the SL M40 if you want the Monogram collection's distinctive branding and are willing to invest in that premium detail. The SL 174 is the smarter pick if you prefer subtle luxury without visible logos, or if budget is a primary concern.
Our Recommendation
The Saint Laurent Monogram SL M40 hits the sweet spot for most customers: it's the standard fit that works across a wide range of face shapes, features the coveted Monogram collection's YSL logo detail, and offers excellent prescription compatibility. The medium 54-18-140 measurements make it versatile and comfortable for all-day wear, and the recycled acetate construction balances luxury with sustainability.
At a Glance
Saint Laurent Monogram SL M40/F Sunglasses
Pros:
- Higher bridge fit (16mm vs 18mm) better suited for those who need more nose clearance
- Slightly larger lens width (55mm vs 54mm) for more coverage
- Longer temples (145mm vs 140mm) for better fit on larger heads
- Same Monogram collection aesthetic with YSL logo detail
Cons:
- May sit too high on the nose for those with lower bridges
- Slightly larger overall proportions may overwhelm smaller faces
- Limited color options compared to standard fit
Saint Laurent Classic SL 174 Sunglasses
Pros:
- More affordable price point ($181 vs $302)
- Similar square shape and acetate construction
- Classic collection offers timeless design without logo branding
- Prescription-ready like the M40
Cons:
- Lacks the signature YSL Cassandre logo detail on temples
- Not part of the Monogram collection's premium line
- Less distinctive branding for those who want visible luxury markers
Saint Laurent Monogram SL M94 Sunglasses
Pros:
- Same Monogram collection with YSL Cassandre logo on temples
- Similar premium acetate construction and quality
- Alternative shape option within the same collection
- Comparable price point and luxury positioning
Cons:
- Different frame shape may not suit the same face shapes
- Slightly higher price ($354-$365 vs $302-$307)
- May have different lens depth affecting progressive lens compatibility