To this unit is added the correct substituted resistance, as well as special light baffling material for illumination spread throughout the face of the photocell, and most importantly a VERY EXPENSIVE NARROW PASS / INTERFERENCE FILTER that is SPECIFICALLY MATCHED to the characteristics of the metering cell, as well as to the spectral characteristics of Green dpss Lasers that typically laze at 532.7nm band wavelengths.  The slightest variance of ANY of these parameters was found to give inaccurate readings, however, when this unit is HAND TUNED, and the correct components are used, also the basic unit itself has met several quality inspections to meet the required parameters, the RESULTS ARE OUTSTANDING.  This meter will read ACCURATELY between the measured readings of 1mw to 70mw of beam power provided by a given Green Laser that is being measured.  The accuracy across the entire scale has been maintained WITHIN +/- 5% and most often Much Closer! 

   The reading should be taken with the laser beam pointing in the central portion of the polyethylene diffusion outermost layer at the front end of the Laser Meter.  The beam should not be centered in the corners, nor should it touch the excellent black deckle paint since it WILL DAMAGE THE PAINT due to residual infrared emissions common among dpss Green Lasers, specifically 808nm and 1064nm warming/heating rays.  So the rule is STAY OFF OF THE PAINT with your laser pointing ONLY at the Milky-White outermost plastic on the face of the meter, and as much centered from left to right and up and down as possible.  The reading should not vary much if you are off a little to the left or right along the LONG DIMENSION of the cell stack.  And for more powerful lasers being tested it is recommended to scan a little across the longer dimension of the cell to avoid damaging the photocell underneath as well as to verify the average reading given.  Each Unit comes with a Leather Case and short handstrap to avoid drop damage.  Acceptable form of payment is Personal/Business Checks or Money Orders or MoneyGram or Western Union or PAYPAL ($4 Surcharge).  Shipping to the 50 States INSURED is $6.95 and to Canada, Europe, U.K. and AustralAsia is $16.50 by REGISTERED U.S. AIRMAIL INSURED.  You will not find a more accurate or convenient and economical to use Green Laser Meter in the current marketplace.  - D.K.A./scientificos