tmat2x4< float, mediump > mediump_mat2x4
2 columns of 4 components matrix of medium precision floating-point numbers. 
OpenGL Mathematics (glm.g-truc.net) 
tmat2x4< float, lowp > lowp_mat2x4
2 columns of 4 components matrix of low precision floating-point numbers. 
tmat2x4< float, highp > highp_mat2x4
2 columns of 4 components matrix of high precision floating-point numbers.