A: In 1909-1910, William G. Allen patented a method of cold-forming screw heads around a hexagonal die. The first trademarked hex key in the US was made by Allen Manufacturing and the name has been used ever since.

Numerical aperture formula

Laser sources are valued for the large amount of power they deliver. However, one of their characteristics is that the beams they produce have small divergences. This can be a limitation for those who require a powerful illumination over a wide angle. To address this issue, we have developed the NA converter, that modifies the geometry of an input fiber guided light beam. Both the numerical aperture and the beam diameter are affected : their product is a constant, so called Lagrange invariant.

The chart below offers the best substitute for popular allen wrench sizes from both Imperial to Metric and Metric to Imperial. Be aware that using a smaller size key will increase the chance of stripping the hardware. For some applications, you may want to try using a larger size key than the one recommended in the chart to see if it fits. When substituting sizes, there isn't always a perfect counterpart and it's best to have both Metric and Imperial allen wrench sets available.

Na of lensformula

The typical application in optogenetics is when the laser source is coupled to an NA 0.22 fiber-optic while the fiber-optic cannula of interest is made of a fiber-optic with NA 0.48. In this case, a magnification of x2.2 is well suited. In this example, with NA converter, the light going out of the output fibre will get twice of the input NA, i.e. 0.48 and fullfil the optical fibre NA.NA converter is based on same design as the Connectorized U-bracket, then can also accept filter insert with attenuating or spectral filters. As a matter of fact, any filter can be fitted to our standard filter holder and its code can be engraved on its body. In this way you can build your set using off the shelf and custom filters.The narrow band filters can be useful for filtering the fluorescence excitation spectrum or for the fluorescence light.

A: An Allen wrench is a tool that's used for installing and removing socket or hex head fasteners, such as set screws and socket head cap screws. They are usually L-shaped, however there are other styles available.

Short Arm SAE Allen Wrench Dimensions (Hex Key) Hex Allen Key Sizes Click on the size to shop products Width Across Flats Length of Long Arm Length of Short Arm Max Min 0.028" 0.028" 0.0275" 1.219" 0.219" 0.035" 0.035" 0.0345" 1.219" 0.344" 0.050" 0.050" 0.049" 1.656" 0.531" 1/16" 0.0625" 0.0615" 1.75" 0.562" 5/64" 0.0781" 0.0771" 1.875" 0.609" 3/32" 0.0937" 0.0927" 2" 0.656" 7/64" 0.1093" 0.1077" 2.125" 0.703" 1/8" 0.1250" 0.1235" 2.25" 0.75" 9/64" 0.1406" 0.1391" 2.375" 0.796" 5/32" 0.1562" 0.1547" 2.5" 0.844" 3/16" 0.1875" 0.1860" 2.75" 0.938" 7/32" 0.2187" 0.2172" 3" 1.031" 1/4" 0.250" 0.248" 3.25" 1.125" 5/16" 0.3125" 0.3110" 3.75" 1.25" 3/8" 0.375" 0.373" 4.25" 1.375" 7/16" 0.4375" 0.4355" 4.75" 1.5" 1/2" 0.50" 0.04975" 5.25" 1.625" 9/16" 0.5625" 0.56" 5.75" 1.75" 5/8" 0.625" 0.6225" 6.25" 1.875" 3/4" 0.75" 0.747" 7.25" 2.125" 7/8" 0.875" 0.872" 8.25" 2.375" 1" 0.050" 0.049" 1.656" 0.531"  * Additional Imperial sizes are available on our website. Short Arm Metric Allen Wrench Dimensions (Hex Key) Hex Allen Key Sizes Click on the size to shop products Width Across Flats Length of Long Arm Length of Short Arm Max Min Max Min Max Min 0.9 0.899 0.876 34 28 11 6 1.3 1.270 1.244 44 39 16 11 1.5 1.5 1.47 45 43 14 13 2 2.00 1.97 50 48 16 15 2.5 2.50 2.47 56 53 18 17 3 3.00 2.96 63 60 20 18 4 4.00 3.96 70 66 25 23 5 5.00 4.96 80 76 28 26 6 6.00 5.95 90 86 32 30 8 8.00 7.95 100 95 36 34 10 10.00 9.95 102 106 40 38 12 12.00 11.95 125 119 45 43 14 14.00 13.95 140 133 56 53 17 17.00 16.93 160 152 63 60 19 19.00 18.93 280 271 70 67 * Additional Metric sizes are available on our website. Long Arm SAE Hex Key Dimensions (Hex Key) Hex Allen Key Sizes Click on the size to shop products Width Across Flats Length of Long Arm Length of Short Arm Max Min 0.050" 0.050" 0.049" 2.844" 0.531" 1/16" 0.0625" 0.0615" 3" 0.562" 5/64" 0.0781" 0.0771" 3.188" 0.609" 3/32" 0.0937" 0.0927" 3.375" 0.656" 7/64" 0.1093" 0.1077" 3.562" 0.703" 1/8" 0.1250" 0.1235" 3.75" 0.75" 9/64" 0.1406" 0.1391" 3.937" 0.796" 5/32" 0.1562" 0.1547" 4.125" 0.844" 3/16" 0.1875" 0.1860" 4.5" 0.938" 7/32" 0.2187" 0.2172" 4.875" 1.031" 1/4" 0.250" 0.248" 5.25" 1.125" 5/16" 0.3125" 0.3110" 6" 1.25" 3/8" 0.375" 0.373" 6.75" 1.375" 7/16" 0.4375" 0.4355" 7.5" 1.5" 1/2" 0.50" 0.04975" 8.25" 1.625" 9/16" 0.5625" 0.56" 9" 1.75" 5/8" 0.625" 0.6225" 9.75" 1.875" 3/4" 0.75" 0.747" 11.25" 2.125" 7/8" 0.875" 0.872" 12.75" 2.375" 1" 0.050" 0.049" 14.25" 0.531" * Additional Metric sizes are available on our website.   Long Arm Metric Allen Wrench Dimensions (Hex Key) Hex Allen Key Sizes Click on the size to shop products Width Across Flats Length of Long Arm Length of Short Arm Max Min Max Min Max Min 1.5 1.5 1.47 78 76 14 13 2 2.00 1.97 83 81 16 15 2.5 2.50 2.47 90 87 18 17 3 3.00 2.96 100 97 20 18 4 4.00 3.96 106 102 25 23 5 5.00 4.96 118 114 28 26 6 6.00 5.95 140 136 32 30 7 7.00 6.97 145 140 36 34 8 8.00 7.95 160 155 36 34 10 10.00 9.95 170 164 40 38     * Additional Metric sizes are available on our website.   Torx/Star Tamper Proof L Key Dimensions Drive Size Click on the size to shop products Length of Short Arm Length of Long Arm T-6 0.5" 1.65" T-7 0.55" 1.75" T-8 0.6" 1.85" T-9 0.65" 2" T-10 0.7" 2.1" T-15 0.75" 2.2" T-20 0.8" 2.35" T-25 0.85" 2.5" T-27 0.95" 2.75" T-30 1.05" 3" T-45 1.25" 3.75" T-50 1.35" 4.25" T-55 1.5" 4.75"   Allen Wrench / Hex Key Conversions The chart below offers the best substitute for popular allen wrench sizes from both Imperial to Metric and Metric to Imperial. Be aware that using a smaller size key will increase the chance of stripping the hardware. For some applications, you may want to try using a larger size key than the one recommended in the chart to see if it fits. When substituting sizes, there isn't always a perfect counterpart and it's best to have both Metric and Imperial allen wrench sets available. Hex Key / Allen Wrench Conversion Chart SAE Conversion for MM MM Conversion for SAE 5/64" 2 mm 2 mm 3/32" 3/32" 2.5 mm 2.5 mm 7/64" 7/64" 3 mm 3 mm 1/8" 1/8" 3.5 mm 3.5 mm 9/64" 5/32" 4 mm 4 mm 5/32" 3/16" 5 mm 5.5 mm 7/32" 7/32" 5.5 mm & 6 mm 6 mm 1/4" 1/4" 7 mm 7 mm 9/32" 5/16" 8 mm 8 mm 5/16" 3/8" 10 mm 9 mm 3/8" Frequently Asked Questions  Q: What is an Allen Wrench used for?  A: An Allen wrench is a tool that's used for installing and removing socket or hex head fasteners, such as set screws and socket head cap screws. They are usually L-shaped, however there are other styles available. Q: Is an Allen wrench the same as a hex key? A: Yes, an Allen wrench is the same as a hex key. They are also called L-Keys, L-Wrenches, Allen Keys Q: Why are they called Allen Wrenches? A: In 1909-1910, William G. Allen patented a method of cold-forming screw heads around a hexagonal die. The first trademarked hex key in the US was made by Allen Manufacturing and the name has been used ever since. Q: Are Allen wrenches the same as Torx wrenches? A: No, allen wrenches have a hexagon shape while Torx wrenches have a star shape. Q: What are the types of Allen wrenches? A: L-shaped, T-handle, P-handle, folding hex, ratcheting hex, torque wrench, Allen screwdriver, ball hex Additional Resources Download Allen Wrenches PDF Shop Related Products Allen Wrench Individual KeysAllen Wrench Key Sets Allen Wrench Key Cases