Grenade Parts Guide

Grenades are made up of up to 10 different parts. Unfortunately only 5 of these have models, all of which overlap, and it isn't even possible to tell between every version of each of them visually.
This page just goes over the visual parts, and what you can tell from them. A full, in-depth guide to all parts and how exactly they affect stats can be found here
The visible parts are as follows:
MaterialBlast RadiusChild CountDelivery Trigger

Material

The material depends entirely on the grenade's manufacture and rarity. Manufacturer changes the model, rarity changes the skin.
There are two unique materials, for the Data Scrubber and the Meganade. These share Maliwan's model, but use custom skins.
Torgue materials are the only ones to provide a stat bonus, they all have +2 child grenades.
BanditDahlHyperionMaliwan
TedioreTorgueVladof

Blast Radius

There are four possible blast radius parts: small, normal, large, and extra large.
There is only one model between them however, the large and extra large parts use the model shown on the right.
Because this model is shared the only way to tell which part exactly a particular grenade has is through its stats.

Child Count

There are seven possible child count parts, with bonuses from +0 to +6 extra child grenades.
Again there is only one model, the +4 to +6 parts all share the one shown on the right.

Delivery

There are seven standard delivery parts.
There are only three different models however, because the lobbed delivery doesn't have a model, and because sticky deliveries share the model of their base version.
The standard deliveries provide minor changes to fuse time. Check the full guide for more info.
HomingLongbowRubberized
There are two unique deliveries with models, the Contraband Sky Rocket uses the "high blast radius" model, and the x4 Magic Missile uses the "high child count" model
Neither of these grenades can spawn with the other parts that share their model.

Trigger

There are six possible trigger parts.
The perfect (lowest fuse) part is the only one with a model, shown on the right.