diff --git a/i6_models/parts/lstm.py b/i6_models/parts/lstm.py
new file mode 100644
index 00000000..e9d6e4d0
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+++ b/i6_models/parts/lstm.py
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+__all__ = ["LstmBlockV1Config", "LstmBlockV1"]
+
+from dataclasses import dataclass
+import torch
+from torch import nn
+from typing import Any, Dict, Tuple, Union
+
+from i6_models.config import ModelConfiguration
+
+
+@dataclass
+class LstmBlockV1Config(ModelConfiguration):
+    """
+    Attributes:
+        input_dim: input dimension size
+        hidden_dim: hidden dimension of one direction of LSTM
+        num_layers: number of uni-directional LSTM layers, minimum 2
+        bias: add a bias term to the LSTM layer
+        dropout: nn.LSTM supports internal Dropout applied between each layer of LSTM (but not on input/output)
+        enforce_sorted:
+            True: expects that sequences are sorted by sequence length in decreasing order.
+                Will not do any sorting.
+                This is required for ONNX-Export, and thus the recommended setting.
+            False: no expectation.
+                It will internally enforce that they are sorted
+                and undo the reordering at the output.
+
+            Sorting can for example be performed independent of the ONNX export in e.g. train_step:
+
+                audio_features_len, indices = torch.sort(audio_features_len, descending=True)
+                audio_features = audio_features[indices, :, :]
+                labels = labels[indices, :]
+                labels_len = labels_len[indices]
+    """
+
+    input_dim: int
+    hidden_dim: int
+    num_layers: int
+    bias: bool
+    dropout: float
+    enforce_sorted: bool
+
+    @classmethod
+    def from_dict(cls, model_cfg_dict: Dict[str, Any]):
+        model_cfg_dict = model_cfg_dict.copy()
+        return cls(**model_cfg_dict)
+
+
+class LstmBlockV1(nn.Module):
+    def __init__(self, model_cfg: Union[LstmBlockV1Config, Dict[str, Any]]):
+        """
+        Model definition of LSTM block. Contains single lstm stack and padding sequence in forward call. Including
+        dropout, batch-first variant, hardcoded to use B,T,F input.
+
+        Supports: TorchScript, ONNX-export.
+
+        :param model_cfg: holds model configuration as dataclass or dict instance.
+        """
+        super().__init__()
+
+        self.cfg = LstmBlockV1Config.from_dict(model_cfg) if isinstance(model_cfg, dict) else model_cfg
+
+        self.dropout = self.cfg.dropout
+        self.enforce_sorted = self.cgf.enforce_sorted
+        self.lstm_stack = nn.LSTM(
+            input_size=self.cfg.input_dim,
+            hidden_size=self.cfg.hidden_dim,
+            num_layers=self.cfg.num_layers,
+            bias=self.cfg.bias,
+            dropout=self.dropout,
+            batch_first=True,
+            bidirectional=False,
+        )
+
+    def forward(self, x: torch.Tensor, seq_len: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
+        """
+        :param x: [B, T, input_dim]
+        :param seq_len:[B], should be on CPU for Script/Trace mode
+        :return: [B, T, hidden_dim]
+        """
+        lstm_packed_in = nn.utils.rnn.pack_padded_sequence(
+            input=x, lengths=seq_len, enforce_sorted=self.enforce_sorted, batch_first=True
+        )
+
+        lstm_out, _ = self.lstm_stack(lstm_packed_in)
+        lstm_out, _ = nn.utils.rnn.pad_packed_sequence(lstm_out, padding_value=0.0, batch_first=True)
+
+        return lstm_out, seq_len