Standard Lens Package

Price includes frames and our standard lens package. Our standard lens package features high-quality CR39 plastic lenses and a durable anti-scratch coating.

If your prescription is stronger than +/- 3.00 we recommend polycarbonate or High Index 1.67 lenses to ensure that your glasses look and feel great.

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Jackknife 4.0 (51) - Polished Black Polished Black Jackknife 4.0 (51) - Pewter Pewter Virtual Mirror Virtual Mirror

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Oakley Jackknife 4.0 (51)

$260.00 more infowith lenses*

Color:

27.9 mm

138 mm

19 mm

51 mm

Frame Only $220.00

Free Shipping + Free Returns Make Buying Easy

We believe that you will be happy with your purchase from AC Lens. We make every effort to provide you with high-quality products and outstanding customer service.

We are so confident in our people and products that we provide you with our 30-Day Guarantee. If you are not 100% satisfied with your purchase, just call our friendly Customer Service Team at 1-888-248-5367 for a Return Authorization. Then, simply return the item in its original condition, including all tags, packaging and accessories and you will receive a prompt exchange or refund.

We even pay for return shipping!*

*Free return shipping is not offered on drop-ship orders. AC Lens retains the right to modify or discontinue this promotion at any time. Free return shipping is limited to a maximum of 3 return shipments in any one year period.

Product Information

Product Reviews

Oakley Jackknife 4.0 (51)

Oakley Jackknife 4.0 eyeglasses are made with the signature O-Metal material, which guarantees quality and comfort. The rims feature a slick semi-rimless design that allows you to see more while also reducing the frame weight.

Oakley Eyeglasses are built with high end craftsmanship for optimal performance. Oakley sunglasses offer sporty designs that use the latest technology to provide comfortable wear that looks as good as it performs.

Brand: Oakley
Frame Type: Semi-Rimless
Frame Shape: Rectangle
Face Shape: Heart
Frame Style: Designer
Gender: Mens
Frame Material: O-Metal

* We are unable to ship this item outside the U.S.

Choose the Best Eyeglass Frames for Your Face Shape

If you already know your facial shape, see below to figure out the best and worst frame shapes to compliment your facial features. If you're not sure what your face shape is, learn how to measure your face shape with our comprehensive guide to face shapes.

Oval face: All frame shapes will compliment your facial features!

Any frame shape should look good
Avoid overtly dramatic frame shapes as they can make your face seem disproportionate
Avoid over sized-frames

Round Face: If your face is round, angular geometric frames help counteract your face's softer features

Rectangle frames
Thin Angular frames
Avoid Tear Drop, Circular, or Cat-Eyed frames

Square Face: Square faces usually benefit most from frames that can soften their naturally boxy geometric shape.

Round Frames
Tear Drop Frames
Avoid Square and Rectangular frames

Heart Shaped Face: Heart shaped faces benefit from frames that add width to the bottom of their face or take away from their forehead.

Circular frames
Rectangular frames
Avoid Cat-Eyed and Tear Drop frames

Diamond Shaped Face: Diamond shaped faces are compatible with most styles, and benefit most from styles that add width to the top and bottom of the face.

Square frames
Rectangular frames
Avoid Circular frames

Oblong Face Shape: People with oblong facial shapes typically benefit most from tall glasses frames that can offset their facial length.

"Aviator" frames
Square frames
Avoid Rectangular or Cat Eyed frames

Find Your Frame Measurements on Your Current Frame

How to Read Your Eyeglasses Frame measurements

Measurements should be three separate digits measured in mm. (example: 45-20-140)

The first value measures the width of the lens

The second value measures the width of the nose bridge

The third value measures the temples (earpieces)

How to Pick a Frame Based Off Your Current Frame Measurements

Write down your current frame measurements.

Find frames within 1-3 mm. of your Lens Width

Find frames within 1-2 mm. of your Nose Bridge Width

Find frames within 4-6 mm. of your temple length

Is This Frame Right for Me?

This frame is versatile and great on most face shapes. For more information on which frames will look best on your face, check out our .

Have a Frame That Fits?

All frames are marked with the eye width, bridge width, and temple length in millimeters. to locate the measurements & find a frame with the same or similar measurements.