How do you change the hitbox size?

Thanks for responding! I saw the page you told me, and I think it may be the way i searched for! But Could you tell me how the size works? he said " this.setSize(0.6F, 1.95F) " But 0.6F = What dimension in minecraft? and also, what is "constructor" he was talking about?

Thanks again! I found the constructor but... Sadly, it doesn't work for me ;-; I am going to try to experiment a bit and i'll tell you if it works. 

It's still not working, and I can't figure out what's wrong... So if you could tell me or help me with the code it would be nice! Hope you will answer!

Here is the code of the mob, if you need something else tell me what and i'll show it to you!

package mod.mcreator;

import net.minecraftforge.fml.relauncher.SideOnly;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.common.registry.EntityRegistry;
import net.minecraftforge.fml.common.event.FMLServerStartingEvent;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;
import net.minecraftforge.fml.common.event.FMLInitializationEvent;
import net.minecraftforge.fml.client.registry.RenderingRegistry;

import net.minecraft.world.biome.Biome;
import net.minecraft.world.World;
import net.minecraft.util.math.MathHelper;
import net.minecraft.util.ResourceLocation;
import net.minecraft.util.EnumHand;
import net.minecraft.util.DamageSource;
import net.minecraft.item.ItemStack;
import net.minecraft.item.Item;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.effect.EntityLightningBolt;
import net.minecraft.entity.ai.EntityAIWander;
import net.minecraft.entity.ai.EntityAISwimming;
import net.minecraft.entity.ai.EntityAILookIdle;
import net.minecraft.entity.SharedMonsterAttributes;
import net.minecraft.entity.EnumCreatureType;
import net.minecraft.entity.EntityCreature;
import net.minecraft.entity.Entity;
import net.minecraft.client.renderer.entity.RenderBiped;
import net.minecraft.client.model.ModelBiped;
import net.minecraft.client.Minecraft;

import java.util.Random;
import java.util.Iterator;
import java.util.ArrayList;

@SuppressWarnings("unchecked")
public class mcreator_mobTest {

    public int mobid = 0;
    public static Object instance;

    public void load(FMLInitializationEvent event) {
    }

    public void generateNether(World world, Random random, int chunkX, int chunkZ) {
    }

    public void generateSurface(World world, Random random, int chunkX, int chunkZ) {
    }

    public int addFuel(ItemStack fuel) {
        return 0;
    }

    @SideOnly(Side.CLIENT)
    public void registerRenderers() {
        RenderBiped customRender = new RenderBiped(Minecraft.getMinecraft().getRenderManager(), new ModelBiped(), 0, 0) {
            protected ResourceLocation getEntityTexture(Entity par1Entity) {
                return new ResourceLocation("templateman.png");
            }
        };
        customRender.addLayer(new net.minecraft.client.renderer.entity.layers.LayerHeldItem(customRender));
        customRender.addLayer(new net.minecraft.client.renderer.entity.layers.LayerBipedArmor(customRender) {
            protected void initArmor() {
                this.modelLeggings = new ModelBiped();
                this.modelArmor = new ModelBiped();
            }
        });
        RenderingRegistry.registerEntityRenderingHandler(mcreator_mobTest.EntitymobTest.class, customRender);

    }

    public void serverLoad(FMLServerStartingEvent event) {
    }

    public void preInit(FMLPreInitializationEvent event) {
        int entityID = MathHelper.getRandomUUID().hashCode();
        mobid = entityID;
        EntityRegistry.registerModEntity(mcreator_mobTest.EntitymobTest.class, "mobTest", entityID, instance, 64, 1, true, (204 << 16) + (204 << 8)
                + 204, (102 << 16) + (102 << 8) + 102);
        EntityRegistry.addSpawn(mcreator_mobTest.EntitymobTest.class, 20, 3, 30, EnumCreatureType.CREATURE, clean(Biome.REGISTRY));

    }

    public static Biome[] clean(net.minecraft.util.registry.RegistryNamespaced<ResourceLocation, Biome> in) {
        Iterator<Biome> itr = in.iterator();
        ArrayList<Biome> ls = new ArrayList<Biome>();
        while (itr.hasNext()) {
            ls.add(itr.next());
        }
        return ls.toArray(new Biome[ls.size()]);
    }

    public static class EntitymobTest extends EntityCreature {
        World world = null;

        public EntitymobTest(World var1) {
            super(var1);

               this.setSize(0.6F, 1.95F);
            world = var1;
            experienceValue = 5;
            this.isImmuneToFire = false;
            addRandomArmor();
            setNoAI(!true);
            this.tasks.addTask(0, new EntityAISwimming(this));
            this.tasks.addTask(6, new EntityAIWander(this, 1.0D));
            this.tasks.addTask(8, new EntityAILookIdle(this));

        }

        protected void applyEntityAttributes() {
            super.applyEntityAttributes();
            this.getEntityAttribute(SharedMonsterAttributes.MOVEMENT_SPEED).setBaseValue(0.25D);
            this.getEntityAttribute(SharedMonsterAttributes.MAX_HEALTH).setBaseValue(10D);
            if (this.getEntityAttribute(SharedMonsterAttributes.ATTACK_DAMAGE) != null)
                this.getEntityAttribute(SharedMonsterAttributes.ATTACK_DAMAGE).setBaseValue(3D);
        }

        protected void addRandomArmor() {

        }

        @Override
        protected Item getDropItem() {
            return null;
        }

        @Override
        protected net.minecraft.util.SoundEvent getAmbientSound() {
            return (net.minecraft.util.SoundEvent) net.minecraft.util.SoundEvent.REGISTRY.getObject(new ResourceLocation(""));
        }

        @Override
        protected net.minecraft.util.SoundEvent getHurtSound() {
            return (net.minecraft.util.SoundEvent) net.minecraft.util.SoundEvent.REGISTRY.getObject(new ResourceLocation("game.neutral.hurt"));
        }

        @Override
        protected net.minecraft.util.SoundEvent getDeathSound() {
            return (net.minecraft.util.SoundEvent) net.minecraft.util.SoundEvent.REGISTRY.getObject(new ResourceLocation("game.neutral.die"));
        }

        @Override
        public void onStruckByLightning(EntityLightningBolt entityLightningBolt) {
            super.onStruckByLightning(entityLightningBolt);
            int i = (int) this.posX;
            int j = (int) this.posY;
            int k = (int) this.posZ;
            Entity entity = this;

        }

        @Override
        public void fall(float l, float d) {
            super.fall(l, d);
            int i = (int) this.posX;
            int j = (int) this.posY;
            int k = (int) this.posZ;
            super.fall(l, d);
            Entity entity = this;

        }

        @Override
        public void onDeath(DamageSource source) {
            super.onDeath(source);
            int i = (int) this.posX;
            int j = (int) this.posY;
            int k = (int) this.posZ;
            Entity entity = this;

        }

        @Override
        public boolean processInteract(EntityPlayer entity, EnumHand hand, ItemStack stack) {
            super.processInteract(entity, hand, stack);
            int i = (int) this.posX;
            int j = (int) this.posY;
            int k = (int) this.posZ;

            return true;
        }

        @Override
        protected float getSoundVolume() {
            return 1.0F;
        }

    }

}

@#8.1 No I just copied the bit of code (this.setSize(0.6F, 1.95F)) in my codes... I don't need to copy everything, do I ?