I'm not a big Glock pistol fan but for custom or after-market Glock parts, I'd get Morgan Boatman's guide;
www.customizeyourglock.com www.boatmanbooks.com www.glockbooks.com .
Morgan Boatman goes into detail about what custom parts or brands do best.
Glockstore.com is Lenny Magill's useful website.
ClydeFrog