The polymer HK433 was initially envisioned as a replacement for the G36 rifle and incorporated some of the features of the HK416. Consequently, the controls on the lower receiver were a hybrid, in order to facilitate transition for customers using either rifle.
They’ve recently changed that direction and now offer dedicated G36 or HK416-style lowers. Here, you can see the G36-style lower.
You may see the 416-style referred to as the HK416E.
An upgrade to the HK433 is intended to assist with chamber checks.
They have introduced a thumb index so that you can get some purchase when conducting chamber check.
In the ejection port side are markings to let the shooter know how far to pull the boot carrier to the ear. Remember, these are intended for military issue.
Finally, the German Bundeswehr is anticipated to make its final procurement decision today regarding a replacement for the G36. You may recall that the Bundeswehr had initially planned to by the Haenel MK556 but a protest by H&K alleging patent infringement stopped the contract. Now, it appears that the German Army will join the KSK in issuing a variant of the HK416.