The BIRR disposable counting chamber BB2-V-20 is specially designed for the assessment of low sperm numbers, like check after vasectomy. Each of the two BB2-V-20 chambers contains a grid, dimensions 10,0 x 5,0 mm. The grid is divided in 5 blocks of 1.0 x 10.0 mm. To improve the finding of the grid the lines are extended at both side 1.5 mm.