The all metal construction of the F is well balanced and easy to control, and it feels really nice in the hand. The head geometry is reminiscent of the Model L in terms of aggressiveness. The F does not really have a spring type mechanism like the more available Model G. Instead, the spring action comes from a copper plate that is riveted to the brass head and sort of acts in the reverse of the plate type spring found on the L. All told, the F is a good shaver, but if someone were to ask me which Injector they should buy, I would point to the Model G. I have F, G, H, I, K, and L Injectors, and a Pal Adjustable and so far, the G is the best shave for me.
Don't reject plastic. To the initial review, I'll just add that if you do in fact want an all metal injector, the type F may be your best bet to get a decent one at a halfway decent price. Other than that, it's a good enough shaver which is outperformed by a number of plastic handled models.
